I’ve had to replace my CentOS 7 server with an AlmaLinux 9. I run my own sendmail service which has been working for many years. Now, I’m not receiving e-mail messages from most outside senders. Strangely, I’m able to get an e-mail from my gmail account via the google e-mail page. I’m not sure why that’s happening, but it may not be related.
Should I be able to connect to my sendmail server via port 25?
I see that sendmail is listening on that port and I can connect to it via telnet on localhost:
telnet localhost 25
lsof -i :25 gives:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
sendmail 3225 root 4u IPv4 24109 0t0 TCP localhost:smtp (LISTEN)
But if I try telnet with my public IP, it gets connection refused:
telnet 65.78.188.61 25
It doesn’t appear to be my firewall (iptables-based) as I’ve stopped the firewall and still cannot telnet to that port.
I used Network Tools: DNS,IP,Email with the TestEmailServer option and it shows the following error:
Connecting to 65.78.188.61
5/5/2024 9:11:24 AM Connection attempt #1 - Unable to connect after 15 seconds. [15.02 sec]
This sendmail configuration has been working for a long time and I can’t see what’s wrong with it now. Can anyone familiar with this please offer some guidance? I’ll share what information you need.