Cannot connect to POP3 on Dovecot

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Problem :

I installed Postfix and Dovecot on Ubuntu 18.04. I tested sending and receiving emails via telnet. Everything works from localhost. This is a droplet on DigitalOcean.

From any remote system, I can telnet to this instance on port 25 but not on 110. This is strange. I can telnet to 110 from the instance itself. Firewall is disabled.

This is the netstat result:

**netstat -anp4 |grep dove**
tcp        0      0 0.0.0.0:110             0.0.0.0:*               LISTEN      24503/dovecot     
tcp        0      0 127.0.0.1:143           0.0.0.0:*               LISTEN      24503/dovecot     
tcp        0      0 0.0.0.0:993             0.0.0.0:*               LISTEN      24503/dovecot     
tcp        0      0 0.0.0.0:995             0.0.0.0:*               LISTEN      24503/dovecot     

From the remote, I get:

Trying 123.123.123.12...

for 60 seconds and then a timeout message.

Solution :

Dovecot defaults to requiring SSL/TLS for all remote logins. If you must use unsecured logins like telnet (or for testing) you must modify /etc/dovecot/10-auth.conf to:

disable_plaintext_auth = no

and modify /etc/dovecot/10-ssl.conf:

ssl = no

then restart Dovecot.

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