Symptoms

JIRA fails to send an email message stating:

Attempted test email send.  Log shows the following (this is the top  of the output):
com.atlassian.mail.MailException: javax.mail.MessagingException: 501  Syntax: HELO hostname
....

Cause

The server's hostname is not set. JIRA is sending the server's IP address instead.

Resolution

Resolutions include:

1. Refer to your system's documentation to set the hostname correctly.
2. Alternatively, add an entry in /etc/hosts.
3. If this doesn't work, pass the hostname to JIRA specifically.

See Problems Sending Email from JIRA - EHLO requires domain address for details.