Jira Mail Queue and SMTP test

Question

I have a problem with notifications. I did not change the configuration, and today notifications reach the queue and are not sent to users. I performed activities from other popular community submissions. In addition, in the SMTP configuration test, the user receives a timeout message:
SocketTimeoutException: Read timed out

I checked a lot for ex.:

https://community.atlassian.com/t5/Questions/JIRA-notification-mail-stuck-in-queue/qaq-p/242174

https://confluence.atlassian.com/doc/the-mail-queue-151387.html

https://confluence.atlassian.com/jirakb/mail-queue-never-flushed-automatically-268045859.html?_ga=2.182059815.122918892.1550750477-1780694437.1550750477

https://community.atlassian.com/t5/Jira-questions/Mails-not-leaving-mail-queue/qaq-p/346757

Thanks for your help

Bartosz Posiakow · Answer

I also used telnet and nc command. It works fine too.

Bartosz Posiakow · Answer

Hello,

I tried to ping SMTP host address and it works fine. How should I check that?

Josh Steckler · Answer

The error you are getting makes me suspect a firewall or other networking issue may be the cause. Have you confirmed that your SMTP server is accessible from the Jira server on the port you are using?