Smtp ошибка 503 valid rcpt command must precede data

Verify the email before resending to eliminate the error

by Afam Onyimadu

Afam is a geek and the go-to among his peers for computer solutions. He has a wealth of experience with Windows operating systems, dating back to his introduction… read more


Updated on May 17, 2023

Reviewed by
Alex Serban

Alex Serban

After moving away from the corporate work-style, Alex has found rewards in a lifestyle of constant analysis, team coordination and pestering his colleagues. Holding an MCSA Windows Server… read more

  • The 503 valid RCPT command must precede data error, makes it impossible to successfully deliver emails.
  • Bad emails are a major trigger, and ensuring they do not contain any special characters will come in handy.

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If you encounter the error message 503 valid rcpt command must precede data, it usually means there’s a problem with the recipient (RCPT) command during SMTP (Simple Mail Transfer Protocol) communication.

Many email senders using SMTP servers like Outlook 365 (Office 365) often encounter this error. So, in this guide, we walk you through the best solutions.

Why do I get the 503 valid RCPT command must precede data in Outlook?

There are a few things that will trigger this error in Outlook, including the following:

  • Incorrect recipient address – If the email address you are trying to send to is incorrect, it may cause the Outlook or Microsoft 365 error.
  • SMTP authentication – If your SMTP server requires authentication and you have provided the correct username and password, it triggers the 503 error.
  • SMTP server configuration – Users who have not correctly configured the email client or application to use the correct SMTP server may get the error.
  • Network connectivity – Sometimes, a slow or bad network connection will cause an Outlook error.

How do I fix the 503 valid rcpt command must precede data error?

Before you proceed with the solutions in this guide, do the following:

  • Verify your internet connection – You may have to use a wired connection or change your ISP to guarantee a good connection.
  • Restart all applications – Sometimes relaunching your apps may fix tiny bugs; you may also consider rebooting the device.
  • Disconnect your VPN – It is recommended that any VPN be disconnected as they may have rigorous firewall or security configurations that can block the necessary ports or protocols.

However, if you are unsuccessful after using the above pre-solutions, proceed to more detailed fixes below.

1. Configure the SMTP Authentication

  1. Log in to Outlook.
  2. Click on the Settings icon and select View all Outlook settings.
    503 valid rcpt command must precede data
  3. Click Mail, then select Sync mail.
    503 valid rcpt command must precede data
  4. Set the SMTP settings to the value below:
    Server name: smtp.office365.com
    Port: 587
    Encryption method: STARTTLS

2. Check Mailbox capacity

  1. Log in to Outlook.
  2. Click on the Settings icon and select View all Outlook settings.503 valid rcpt command must precede data
  3. Click on General, then select Storage.
    503 valid rcpt command must precede data
  4. If you are out of storage, on the right pane, click Get more storage and follow the prompt.
    503 valid rcpt command must precede data
  5. Verify if it fixes the 503 valid RCPT command must precede data error.
Read more about this topic

  • Fix: the new Outlook could not successfully launch error
  • Emsmdb32.dll Crashes Outlook 365: How to Fix it

3. Check the email address

The email address you used in the From field is visible to the recipient when you send an email. Using a different email address than the one in your outgoing mail settings may lead to authentication problems and error 503.

Also, it’s important to note that using special characters, such as apostrophes, in email addresses can result in email transmission issues and potentially trigger the Outlook 503 error. To ensure accuracy, you should review and eliminate any special characters or symbols in the recipient’s email address.

4. Fix corrupt PST file

If the Outlook PST file is damaged, you might encounter the error 503. So you can use an advanced PST file repair software like Stellar Repair for Outlook.

We have written a comprehensive guide on using this tool to fix your bad PST files.

With the fixes discussed, you should have successfully fixed the 503 valid RCPT command must precede data error.

Other readers would love to know what worked for you, so please leave us a note in the comments section below.

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If the advices above haven’t solved your issue, your PC may experience deeper Windows problems. We recommend downloading this PC Repair tool (rated Great on TrustPilot.com) to easily address them. After installation, simply click the Start Scan button and then press on Repair All.

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Valid RCPT command must precede DATA: Error 503, can be easily resolved with a little bit of help from the experts at Bobcares.

At Bobcares, we offer solutions for every query, big and small, as a part of our Server Management Services.

Let’s take a look at how our Support Team is ready to help customers resolve Error 503: valid RCPT command must precede DATA.

How to resolve: Valid RCPT command must precede DATA

The Outlook error 503 often pops up when attempting to send an email. This error is an indication that the email server did not accurately authenticate the SMTP connection.

Error 503: Valid RCPT command must precede DATA

According to our Support Techs, the error may be due to either one of the following causes:

    • The email client does not have SMTP Authentication set up.
    • The email server expects us to check email first before sending an email.

Fortunately, our Support Techs are here to help you resolve these issues.

How to set up SMTP Authentication

Although the SMTP Authentication set up depends on the email client we are using, here is how we can get it done in Outlook:

  1. First, open Outlook 2016.
  2. Then, head to the File menu and navigate to Account Settings > Account Settings.

    Error 503: Valid RCPT command must precede DATA- Outlook settings

  3. Then, choose the email account we want to set up and click Change.
  4. After that, choose More Settings.. in the Change Account window.
  5. Next, navigate to Outgoing Server > My outgoing server (SMTP) requires authentication > Use same settings as my incoming mail server and select the Advanced tab.
  6. Then, we have to set the Outgoing server (SMTP) port value to 465. After that, we have to select SSL in the Use the following type of encryption drop-down list and click Ok.
  7. Finally, click Next in the Internet E-mail Settings and click >strong>Finish.

How to check email before sending

When we first open our email client, it checks email first automatically. However, if we send an email after around thirty minutes and see the Error 503 message, we have to check the email for new messages. This will allow us to send an email without any further problems.

[Looking for a solution to another query? We are just a click away.]

Conclusion

In brief, our skilled Support Engineers at Bobcares demonstrated how to resolve Error 503: valid RCPT command must precede DATA.

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Ниже вы можете узнать о возможных причинах сбоя при отправке почты.

Чаще всего ошибка с отправкой писем возникает в следующих случаях:

  1. Неверно указан адрес получателя. В данном случае вы получите обратное письмо о том, что данный почтовый ящик или домен не существует. (Ошибка 505)
  2. Превышены показатели ограничений на отправку. С ограничениями Вы можете ознакомиться на нашем сайте.
  3. Окончание почтовой квоты для данной э-почты. Решение проблемы вы сможете найти здесь.
  4. Ошибка в настройке почтовых клиентов. Проблема устраняется исправлением ошибок. С полными настройками для почтового клиента вы можете ознакомится здесь.

Самые распространенные ошибки в данном случае:

Error 503: valid rcpt command must precede data — требует подтвердить подлинность SMTP сервера. К примеру в Outlook это можно сделать поставив галочку напротив пункта «My server requires authentication» в настройках сервера исходящей почты.

Error 553 unable to verify address — так же требует подключить проверку подлинности SMTP сервера. Пожалуйста обратите внимание на то что в поле «Имя пользователя» необходимо ввести полный адрес электронной почты, к примеру [email protected].

Ниже вы можете узнать о возможных причинах сбоя при отправке почты.

Чаще всего ошибка с отправкой писем возникает в следующих случаях:

  1. Неверно указан адрес получателя. В данном случае вы получите обратное письмо о том, что данный почтовый ящик или домен не существует. (Ошибка 505)
  2. Превышены показатели ограничений на отправку. С ограничениями Вы можете ознакомиться на нашем сайте.
  3. Окончание почтовой квоты для данной э-почты. Решение проблемы вы сможете найти здесь.
  4. Ошибка в настройке почтовых клиентов. Проблема устраняется исправлением ошибок. С полными настройками для почтового клиента вы можете ознакомится здесь.

Самые распространенные ошибки в данном случае:

Error 503: valid rcpt command must precede data — требует подтвердить подлинность SMTP сервера. К примеру в Outlook это можно сделать поставив галочку напротив пункта «My server requires authentication» в настройках сервера исходящей почты.

Error 553 unable to verify address — так же требует подключить проверку подлинности SMTP сервера. Пожалуйста обратите внимание на то что в поле «Имя пользователя» необходимо ввести полный адрес электронной почты, к примеру name@mydomain.com.

For those that are tearing their hair out when getting the “503 valid RCPT command must precede DATA” error (we’ll refer to it as simply the 503 error going forwards) when trying to send email, here are some common solutions that will hopefully get you back up and running. If these don’t work, or you need more detail on any of these steps, please read the rest of this article, and its comments, for some more in-depth solutions.

  • Apostrophes – remove any apostrophes (single quotes) or other non-alphabetic characters from your email account name(s).
  • VPN – if your system is trying to connect via a VPN network while you’re sending email, you may get this error. Try disconnecting the VPN before sending/ receiving mail.
  • Full mailbox – make sure the mailbox of the affected account is not full or has met/ exceeded its quota. You can uncheck the following option to make sure a copy of all your emails is not being left on the server (note that since the email will be downloaded to your PC after this setting change, you won’t be able to access your emails from another location if you do this). In Outlook, browse to Tools > Account Setting > More settings > Advanced > uncheck “leave a copy of this message on the server.”
  • SMTP port – use port 26 (instead of the default 25) for outgoing mail.
  • Server authentication – setup your outgoing mail to use outgoing server authentication (sends mail by logging in with your email address and password). In Outlook, browse to Tools > Account Settings > More settings > Advanced and change the outgoing server to ‘Auto.’ Next, browse back to More settings > Outgoing server and check the “My outgoing server uses the same authentication as my incoming server” box. If you select to have Outlook “remember your password” you won’t have to type it in every time you send an email.
  • Sender matching – make sure you’re sending from the same email address that the recipient sees your email coming in as (ie. don’t make the “from” field differ from the email address used in your outgoing mail settings).
  • Outlook PST files – sometimes the 503 error will occur if you have a corrupt outlook PST (mail archive) file. Try repairing the file.

If none of these approaches work, or you need more detail on a particular step, please read the rest of this article for some additional suggestions.

Option: Use Spam Bully for Outlook and Outlook Express

The 503 valid RCPT command must precede DATA error is a common one that often occurs as a result of the spam software you’re using, or as a result of Outlook’s default spam utility. We recommend giving Spam Bully a try. You can try it for free, and it’s one of the better known and more powerful spam filters. You can nail two birds with one stone – get rid of this annoying error and get rid of your annoying spam messages at the same time. Look at the error as a blessing – it helped you find Spam Bully :).

We recently got this error when trying to send an email in Outlook. The culprit? Apparently this occurs when a server is expecting to receive mail before sending. This is usually results from server authentication priorities (for example, you attempt to send mail before your “spam filter” has finished its receiving process.)

Solutions to resolve the 503 RCPT error

  • Pop before SMTP — Run a check for new messages (F9 key in Outlook) before sending your message and restart and rerun your spam filter application. Your IP address is entered in a relayhosts file, allowing email to be sent from your address for up to half an hour.
  • If the problem still persists check “my server requires authentication” to authenticate automatically. With this setting you can bypass the check above and send mail without having to “pop” your mail box first. You can also try changing the outgoing port from 25 to 26, since some ISP’s block this port.
  • Several of our readers have pointed out that it may help to remove apostrophes from your email account names (and ask senders to remove them if you’re having trouble receiving emails from them).
  • If you’re on a VPN, try disconnecting from the VPN prior to using your mail program.
  • Your mailbox may be full – try clearing out messages or asking your mail service provider to increase your mailbox limits.
  • If you are using multiple mailboxes, make sure these fixes/ settings are applied to each one of them, especially the “default” one.
  • Finally, if using a mail screening utility such as Mail Washer, you may want to disable the “automatically check at intervals” setting and check mail manually. If the system checks mail while you are sending you may get this error.

If these don’t work, check your mail server

If none of the above work we recommend contacting your hosting provider. Your mail services account needs to be set up properly (associated with the right user name, etc.). We encountered this exact problem when switching hosts once – the mail server configuration got goofed up, and none of the above solutions worked. In the interim (until settings are fixed by your hosting provider) you can adjust your outgoing mail server to reflect that which your ISP uses, which should let you send mail again through your local client (Outlook, but not from the server (Webmail)), until the problem is fixed.

Install anti-spam software

As mentioned previously, to keep your mail system running smoothly, and to help you get rid of various email related errors, including the 503 valid RCPT error, we recommend installing a solid anti-spam solution. Anti-spam software is affordable, but your email and privacy are priceless. Don’t let the spammers get the best of you. For a limited time, get a free trial of Spam Bully.

  • Created
    May 14, 2021
  • Category
    HostPapa Email

The Outlook Error 503 Valid RCPT command must precede DATA can occur when sending an email. It’s telling you that your email server did not properly authenticate your SMTP (outgoing mail) connection.

The two most common causes for this error are:

  • Your email server requires you to check email first before sending an email (checking email first is one way your email provider manages the security of your email account).
  • Your email client isn’t set up for SMTP Authentication.

Follow these steps to fix the Outlook Error 503 Valid RCPT command must precede DATA error on your email server. These steps will work for Outlook 2016, Outlook 2019, and Outlook 365.

Checking email before sending

When you first open your email client, it automatically checks your email first. However, if you attempt to send an email after about 30 minutes and see this message, simply check your email for new messages. You’ll then be able to send an email if this is the problem (most common with Outlook).

More often, Outlook Error 503 tells you that you need to set up SMTP Authentication in your email client.

Setting up SMTP Authentication

Configuring SMTP Authentication in your email client requires you to edit your email account SMTP (outgoing mail) settings. Add your email address and password to the SMTP settings, and you won’t receive any more Outlook Error 503 Valid RCPT command must precede DATA messages.

How you set up SMTP Authentication depends on the email client you use. Here’s how to set it up in Outlook:

  1. Open Outlook 2016.
  2. Open the File menu and select Account Settings > Account Settings.
    SMTP Authentication in Outlook 2016
  3. In the Account Settings window, select the email account you wish to set up and click Change…
    SMTP Authentication in Outlook 2016
  4. In the Change Account window, click More Settings…
    SMTP Authentication in Outlook 2016
  5. From the More Settings window, select the Outgoing Server tab.
  6. Check My outgoing server (SMTP) requires authentication.
  7. Select Use same settings as my incoming mail server.
  8. Open the Advanced tab.
  9. In the Advanced tab, set the Outgoing server (SMTP) port to 465. In the Use the following type of encryption drop-down, select SSL.
  10. Click OK.
  11. On the Internet E-Mail Settings window, click Next.
  12. Click Finish.

If you need help with your HostPapa account, please open a support ticket from your dashboard.

Customers who use Outlook to access email accounts hosted on cPanel/WHM email servers sometimes report the error 503 Valid RCPT command must precede DATA when trying to send their mails.

This is often reported for servers in which SMTP authentication is enabled.

What is this error?

503 Valid RCPT command must precede DATA essentially means that the server was unable to accept the message, usually because the SMTP connection was not properly authenticated.

In cPanel/WHM servers, authentication can happen either through POP-before-SMTP or through SMTP authentication. If the user has not configured Outlook for outgoing mail SMTP authentication, and has not connected to the POP server before sending the mail, this error is returned.

[ Need help resolving email errors in your sites? Get assistance from our server experts to fix your website. ]

How to fix this error

SMTP authentication is enabled by default in cPanel/WHM servers. So, the fastest way to resolve this error is to enable SMTP authentication for the email account. Here’s how to do it in Outlook.

1. From the Menu Bar, Click Tools then Click E-mail Accounts
2. Select "View or change existing e-mail accounts" then Click "Next"
3. Select the Email account and click "Change"
4. Click "More settings"
5. Select the "Outgoing Server" tab
6. Select the box beside "My outgoing server (SMTP) requires authentication"
7. Select "Use same settings as my incoming email server"
8. Click OK, Next and then Finish.

NOTE : In Outlook 2010 and later, the Email account can be selected by going to Menu bar >> File >> Info tab >> Account Settings

Alternatively, if your server does not allow SMTP authentication, ask your customer to POP their mail before trying to send mails.

[ You don’t have to lose your sleep over lost emails. Get our professional help to fix your mail errors. ]

Still not fixed?

There are a few uncommon causes for this error. Here are the fixes for them:

1. Symbols in username – If the username has any kind of non-alphanumeric characters, try removing that.
2. User behind a corporate VPN – Some VPN configurations are known to mess with the connection initiation. Ask the customer to try connecting without the VPN.
3. Email filter in the PC – Some email firewalls are known to interfere with the connection. If the customer has installed a new email firewall or has made a recent update in security rules, that could be the cause.
4. SMTP port block in ISP – If your customer uses port 25 to connect to your server, ask them to try using the alternate Exim port 26. Maybe the connection is being disrupted by an ISP port 25 block.
5. Corrupted Outlook profile – If all of the above checks are OK, the Outlook profile might be corrupt. Re-adding the account into Outlook or repairing the Outlook PST file using “Microsoft PST repair tool” can fix the issue.

Email errors are the most common category of issues reported by cPanel/WHM account owners. Bobcares helps cPanel account owners quickly recover from service issues, and avoid business downtime.

[ Are your users complaining about email errors? Get our server specialists’ assistance to fix your mail server. ]

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The “503 Valid RCPT command must precede DATA” error mainly occurs when your email server didn´t properly verify your SMTP (outgoing mail) connection. It can also appear if there´s an antivirus or firewall software checking your mail connections.

This type of error can cause a lot of problems while trying to send emails (especially when using Outlook).

How to solve the error 503

Because this error is more common on Outlook, first we´ll explain how to fix it first via your Outlook account.

  1. Access your outlook account´s configuration: go to File- Account settings
  2. Then go to more settings
  3. Click on the outgoing server tab and select My outgoing server (SMTP) requires authentication.
  4. Choose the Use same settings as my incoming mail server
  5. Finally, select the advanced tab and select an outgoing server port and choose your type of encryption. Then press ok to save the settings

If you come across this error outside Outlook or if the previous steps didn´t work, there are a few things you can do to mend it:

  • If you´re using a VPN to navigate and receive this error, disconnect immediately.
  • Use a different SMTP port. Use port 26 instead of the default 25. Some broadband providers block the 25 port for SMTP mail. In that case, you can use the alternative non crypted 587 port or the 465 port with crypted SSL connection.
  • Check your email before sending: when you open your email client, it automatically checks your email first. But if you try to send an email and see the error pop up, just check if you´ve received new emails. It should then let you send the email if it´s the problem  
  • Set up SMTP authentication: add your email address and password to the SMPT settings and chances are you won´t receive the 503 Valid RCPT command must precede DATA error message again.

How to set up SMTP authentication?

The most common thing is that the Error 503 is a sign to tell you to set up SMTP authentication in your email client.

You can do this several ways depending on the email client you use. I´ll teach you how to do it in Thunderbird V52.

  1. In the Tools menu select Account Options.
  2. Go to the bottom and click Outgoing Server
  3. Select the SMTP server you want to change and click the Edit button
  4. In the SMTP tab, set Connection security to SSL/TLS, Authentication method to Normal password, then enter your email address.
  5. Finally, press OK to save the settings

When re-entering to check your email, you´ll be asked for your account password. Enter the password and press Save password.

I hope this article was usefull. If you have any questions let us know and please check us out at Obambu.com for more web related services.

Alejandro Prieto

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