Environment: CentOS, Postfix, Dovecot, Digital Ocean Droplet
Background: The mail server I just installed appears to send and receive normally. I tested my website on MXtoolbox and received 1 error that was related to SMTP. It was the only error that I received.
Unable to Connect to SMTP Host
Description: We attempted a connection to your mail server on port 25 but your server did not respond. More than likely there is no email server at this address or you have a misconfigured firewall or spam filtering system.
Question: Firewalld is blocking port 25. The only ports I have open are,
80/tcp 443/tcp 587/tcp 993/tcp. Do I need port 25 to be open for the mail server to function correctly and consistently or is this error unimportant?