Sending Email Fails Due to 501 Syntax: HELO Hostname Error
Platform Notice: Data Center - This article applies to Atlassian products on the Data Center platform.
Note that this knowledge base article was created for the Data Center version of the product. Data Center knowledge base articles for non-Data Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.
*Except Fisheye and Crucible
Symptoms
The following error is logged in Confluence or JIRA logs:
An error has occurred with sending the test email:
com.atlassian.mail.MailException: javax.mail.MessagingException: 501 Syntax: HELO hostnameSome variations of the same error:
Unable to connect to the server at exchange.company.com due to the following exception: javax.mail.MessagingException: 501 Syntax: HELO hostnameCause
Server's hostname is not defined, so Confluence or JIRA sends the server's IP address instead of the hostname on the HELO SMTP command.
Resolution
Edit /etc/hosts file (or C:\Windows\system32\drivers\etc\hosts) adding an entry to convert your computer's IP to its hostname. It will be something like:
192.168.132.27 exchange.company.comThis can be fixed as well on the DNS server. Indeed, make sure JIRA is using the correct DNS server.