Recently I get the this error below when I testing SMTP 25 port on my email server and I want to share that issue with you: 220 ****************************
When I send email to external email server and vice versa all messages stayed in queue. After that I checked telnet smtp port from internal and external then I released that telnet session to our mail server on port 25 return that error above. Email server use Cisco as a firewall and mail flow happens over that. On Cisco firewall has a feature SMTP fixup and that was enabled. After disable that option all problems gone.
To fix that You must to login your firewall and select Configuration tab -> Firewall button, then select Service Policy Rules. Edit inspection_default policy and Disable ESMTP option.
After that I test my telnet and I could send helo and ehlo command and receive required response.
If You have any question about this or another topic Please feel free contact with us. You can also ask to create specific articles which you want to see on our blog.
