Link to home
Start Free TrialLog in
Avatar of GWIC100
GWIC100Flag for United States of America

asked on

telnet to port 25 on mail server hangs for over 1 minute before responding with 220

My mail server was working great two days ago. something changed over night. Now when I telnet 25 the system hangs for over a minute before it gives me a 220 message.

I suspected DNS was the issue and that's why I used the IP address. If I telnet to localhost 25 on the mail server, it is very quick, but if I telnet 25  or telnet mailhostname 25 it hangs for just over 1 minute before giving me a 220 message.

any ideas?

- I can ping mailhostname and get quick responce, I'm thinking it's a sendmail configuration issue...
Avatar of jar3817

Are you doing this locally? Obviously when you did the localhost:25 connection it was, but what about when you use the name or ip? If not, does it act the same from a lan client? How about an internet client? Does this server use any dns blacklists for spam control? If so have you checked if the lists are all functioning and responding quickly? Are the resolvers in /etc/resolv.conf all functioning properly?
could your firewall be slowing things down maybe ?
try elimination
does it respond the same from other computers ? if so then the prob is most likely with the mail server..

check firewall / sendmail logs for clues.

you could take a look at this ( though not for sendmail )

Usually it is DNS issue.
The smtp server upon client connection tries to solve the client's IP to real name (some mta then check if the name resolved back to same IP).
In other words the server where smtp server lives has to be able to resolve Your IP from reverse DNS.
Do I make sense or You need more clarifications?
Avatar of GWIC100


Here is the answer I found.

At the beginning of the is a disclaimer which says do not edit this file, but the solution I found does just that. I changed the DaemonPortOptions line to read:


Replace with the local ip address of the server and then save and do the following at a shell prompt:

service sendmail restart

Sendmail is now very fast at sending.
In fact it was DNS issue, but another type - refund.
Avatar of DarthMod
Flag of United States of America image

Link to home
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial