This issue applies to any IMail server that is configured to use SSL for outbound messages. There are several solutions to this problem, depending on the version of IMail you are running.IMail Version 12.5.6
1) From the IMail Administrative Console, navigate to Services>IMail Queue Manager.
2) Confirm that you already have "Use SSL" enabled. If this setting is not enabled, you will not be affected by this issue.
3) If "Use SSL" is enabled(recommended), you will need to Enable the "Do not roll over to SSL port 465" option to ensure that your server is not blacklisted.
4) Lastly, restart both the Queue Manager and SMTP Services.IMail Versions 12.5.5 and Earlier:
If you are running a version prior to 12.5.5, you have several options:
1) Upgrade to IMail 12.5.6 and make the settings changes mentioned above.
2) From the IMail Admin Console, disable the "Use SSL" option under Services>IMail Queue Manager. Note: This will cause outbound mail to be sent unencrypted (not recommended).
3) Block all outbound traffic on port 465 using either your network firewall or a software firewall on the server. This will cause connection attempts on 465 to fail and IMail will roll over to the next available encryption method.
4) Restart SMTP and Queue Manager services after making any of the above changes and then test mail delivery.
This does not affect client to server configurations. No changes are required if you use port 465 between your client and the IMail server. This only affects mail being sent outbound from IMail Server to other servers.If you have already been blacklisted:
1) Make the settings changes recommended above and test to ensure mail delivery is working and that outbound connections on port 465 are not possible.
2) Visit the Composite Blocking List(CBL) website https://www.abuseat.org/
and click on the button in the upper right hand corner labelled "Lookup/Remove".
3) Enter the public IP of your IMail Server and click "Lookup".
4) If your IP shows as being blacklisted, follow the instructions from CBL to have you IP listing removed.Note:
At the time of this writing, delisting with CBL appears to be the only requirement, however, It is recommended that you check other common blacklisting sites such as https://www.spamhaus.org
to ensure you have not been listed elsewhere.