Mail server issues Postfix

[Véronique]

Hi,

We are having issues with our outgoing mail server. We are getting error:

An error has occurred with sending the test email:
com.atlassian.mail.MailException: javax.mail.MessagingException: Could not connect to SMTP host: mail.support.eu, port: 587;
  nested exception is:
	javax.net.ssl.SSLException: Unsupported or unrecognized SSL message
...

DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Oracle]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "mail.support.eu", port 587, isSSL true

We have already tried all resolutions that we can find in Atlassian documentation.

Looking at the TCP dump, it seems like Jira is not providing credentials. 

We have set the mail server up in the Jira interface and it looks like Jira is able to connect to the mail server (seeing the feedback at the mailservers side).

Any ideas?