[Gllug] strange SMTP stuff

[Xander D Harkness]

I am a secondary relay for a company in Belgium.

They have a mail server (That is a bit opptomistic - it is a box which 
occasionally decides it would like to receive mail) on IP address 
217.136.235.122

Both mail.broadnet.net and mail.mactelecom.com resolve to this address.

If I run telnet mail.broadnet.net 25

I get a normal SMTP response.

Trying 217.136.253.122...
Connected to mail.broadnet.net.
Escape character is '^]'.
220 corpmail04.broadnetcorp.com ESMTP Server (Microsoft Exchange 
Internet Mail Service 5.5.2650.21) ready
ehlo xanderiam
250-corpmail04.broadnetcorp.com Hello 
[host217-35-85-159.in-addr.btopenworld.com]
250-XEXCH50
250-HELP
250-ETRN
250-DSN
250-SIZE 5242880
250-AUTH LOGIN
250 AUTH=LOGIN
quit

If I run telnet mail.mactelecom.com 25

Trying 217.136.235.122...
telnet: connect to address 217.136.235.122: Connection timed out

I would assume that telnet would use the IP address and there would be 
no hostname passed forward as in a HTTP request.

I have done a packet capture and I do not seem to get a response at all 
from mail.mactelecom.com, just three transmissions to the server.

Does anyone have any ideas why this might be?

There is a simple firewall there, that only filters ports, nothing as 
complicated as hostnames.


Kind regards
Xander



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