Telnet on Sophos SMTP Port 25(TCP)

Question

Hi there, 
 i've got a strange issue, at least for me. 
 Once i had an older versoin of Sophos (I think it was 9.5 or similar) where i was not able to telnet the smtp port of my sophos. Which was fine, as the port was not visible to the outsiders. Nethertheless sophos accepted mails for redirecting it to an internal Linux SMTP server. 
 Today, working in other companies i see that TCP Port 25 is open for telnet on Sophos with similar (in fact the same) configurations like an exchange server for mails. 
 So what's the deal about it? Am i misundertanding something? 
 
 Furthermore, is there a possibility to change the message that appears if i execute "telnet EXTERNALIP 25" , as this gives me the internal hostname and i don't really think that this is a good idea: 
 220 myinternalserver.company.com ESMTP ready.

Jaydeep · Accepted Answer

Hi Rumak18 
 For any device to accept emails, it will have to allow SMTP connection from any IP on the internet (As Sending Email server can be from anywhere). Unless you're accepting an Email from upstream Smart-host only, you will be able to Telnet on External IP on SMTP ports. There's nothing wrong with it.