Problem connecting with desktop client

I run my home server under Rocky Linux 9. The server is modem / router and as such has two firewall interfaces; internal and external.

Dovecot version is dovecot-2.3.16-8.el9.x86_64 kernel is: 5.14.0-284.18.1.el9_2.x86_64

My domain is wo-lar.com

Postfix and Dovecot are up and running, and I can send and receive emails from CLI.

But I cannot connect from desktop clients. I get the following error message: Server message: Can't connect to host "tcp://wo-lar.com:143"

I tried to telnet from my desktop and server. Results are the same:

• I always get a connection refused: telnet wo-lar.com 143 telnet / telnet <Server LAN IP> 143. On server only: telnet 127.0.0.1 143
• telnet wo-lar 143 (without .com!) establishes a connection [root@home wp.rauchholz]# telnet wo-lar 143 Trying 79.152.236.25... Connected to wo-lar. Escape character is '^]'. OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ STARTTLS AUTH=PLAIN AUTH=LOGIN] Dovecot ready.

I went through all kinds for conf files and search for wo-lar string, but can't find it anywhere

Where is the mistake hiding?

Thanks for helping.

Wolfgang