Email fails to be sent or received when Server-Side Synchronization is configured with Gmail

This article provides solutions to errors that occur when Server-Side Synchronization is configured with Gmail.

Applies to:   Microsoft Dynamics CRM 2013, Microsoft Dynamics CRM 2015, Microsoft Dynamics CRM 2016, Microsoft Dynamics CRM 2016 Service Pack 1
Original KB number:   3185281


If Microsoft Dynamics CRM is configured to use Server-Side Synchronization with Gmail, you may receive one of the following error messages:

Email cannot be received for the mailbox <Mailbox Name>. Make sure that the credentials specified in the mailbox are correct and have sufficient permissions for receiving email. Then, enable the mailbox for email processing.

An unknown error occurred while sending the email message "Test Message". Mailbox <Mailbox Name> didn't synchronize. The owner of the associated email server profile <Email Server Profile Name> has been notified.


The errors occur for one of the following reasons:

  • Cause 1

    The email address, username, or password in the mailbox record in Microsoft Dynamics CRM aren't correct.

  • Cause 2

    The correct port isn't configured within the Email Server Profile record in Microsoft Dynamics CRM.

  • Cause 3

    POP isn't enabled on your Gmail mailbox.

  • Cause 4

    A setting in Gmail is preventing Server-Side Sync from authenticating to the Gmail mailbox.


  • Resolution 1

    Verify the values of the Email Address, Username, and Password fields in the mailbox record in Microsoft Dynamics CRM.

  • Resolution 2

    Open the Email Server Profile and then select Advanced. Set the Incoming Port to 995 and the Outgoing Port to 587.

  • Resolution 3

    Follow the Gmail instructions for enabling POP.

  • Resolution 4

    Check your Gmail mailbox for an email about a blocked sign-in attempt. The message will include steps for how to unblock access. After following the steps, try testing and enabling the mailbox in CRM again.

If the issue still occurs, see Troubleshoot sign-in problems, which includes additional steps that may be necessary to enable email access from an app.

More information

The details section of the Alert may include the following text:

"Error : System.Net.Mail.SmtpException: Syntax error, command unrecognized. The server response was:
at System.Net.Mail.SmtpConnection.ConnectAndHandshakeAsyncResult.End(IAsyncResult result)
at System.Net.Mail.SmtpClient.ConnectCallback(IAsyncResult result)"

Third-party information disclaimer

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.