Issue Issue Sending Emails via Plesk Using Mailbox.org SMTP

[sauerleander]

Server operating system version

Ubuntu 24.04

Plesk version and microupdate number

18.0.56 #2

Hello Plesk Community,





I am experiencing an issue where I cannot send emails from my Plesk instance. The instance is configured to use Mailbox.org as the SMTP server on port 465. The credentials work correctly outside of Plesk, so I suspect the problem is related to the Plesk setup itself.





Here are some technical details (sensitive information removed for public posting):

• Web Server: [Web Server Name]
• License: [IONOS SE License – not publicly shared]
• Hosting via IONOS SE

Has anyone encountered a similar issue or can suggest what might be causing this? I can provide additional sensitive details privately if needed for troubleshooting.





Thanks in advance for any guidance or suggestions!





Best regards

 

[Sebahat.hadzhi]

Hi, @sauerleander . The first thing that comes to mind is port 465 being blocked. Have you confirmed it is open on the server and on IONOS' end? Are there any more details you can provide on the experienced issue - errors, logs or bounce back messages?

 

[sauerleander]

Hi @Sebahat.hadzhi,



thank you for your suggestions. I believe the issue is finally resolved. The root cause was that I recently regained multiple domains from my hosting provider and forgot to update the server hostname accordingly.



As a small improvement suggestion, it would be great if Plesk allowed configuring which sender address should be used directly when setting up external SMTP servers. I haven’t been able to find this option yet.



Additionally, I have a few questions:

1. Is HTTP/3 officially supported? I’ve heard from another host that also provides licenses through you that it might still be in some kind of beta.
2. As a customer whose license is obtained via IONOS SE, am I theoretically able to open support tickets directly with Plesk for issues like these?
3. Does the system automatically handle all updates for both Plesk and Ubuntu, including major Ubuntu updates? And what happens with packages that have been installed manually — are they affected or left untouched?

Thanks in advance for your guidance!