Sending Email Fails Due to 501 Syntax: HELO Hostname Error

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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 hostname

Some variations of the same error:

Unable to connect to the server at due to the following exception: javax.mail.MessagingException: 501 Syntax: HELO hostname

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.


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:

This can be fixed as well on the DNS server. Indeed, make sure JIRA is using the correct DNS server.

Last modified on Feb 26, 2016

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