Hey there,

If you aren't having any other networking issues and you haven't changed the email port , it sounds like this might be an issue with your firewall configuration. I recommend that you check your ports, and iptables with the following to help identify the issue:

From a local host

$ nmap $IP

On your Linode

$ sudo iptables -L

Feel free to share your output here if you'd like additional assistance.

Sincerely,
Tara T
Linode Support Team

You may also want to check the MX records in the DNS zone for your domain name. If those are set incorrectly the email messages may be sent to a different mailserver!