NOQUEUE: Null connection from cs24160121-88.houston.rr.com

[Paul Mancillas]

I'm starting to see messages like "NOQUEUE: Null connection from cs24160121-88.houston.rr.com [24.160.121.88]" in the sendmail log. Does anyone know what this message means? Is someone trying to hack into my email server? Does anyone know if there is a "sendmail database" on the Internet where I can look up these types of "error" messages?

Thanks for your reply,

Paul Mancillas

[someone_4 · Accepted solution]

hi ..
Just wondering but what do you get if you do an nslookup to that domain and ip adress? Also do you see anything kind of connection problems when you do the command
#mailq

Here are two links that talk about the same issue you are having. Let us know if this helps.



http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x2fe1f9beca68d511abcd0090277a778c,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xd6fea12d6d27d5118fef0090279cd0f9,00.html

[Paul Mancillas]

Richard,

Thanks for the help. The links you gave were helpful. But I still have a question. Can someone hack into my email server just by using "telnet host 25"? In other words, can they do damage to my system by using only sendmail commands?

Thanks,

Paul Mancillas

[someone_4]

Hey Paul,
I am not 100% sure about that. I know that you can spam and relay mail though your mailserver though port 25 if you are in open relay.And that in its self is a headache if you get blacklisted. But as far as doing major damage though port 25 with sendmail commands. I would say no but once again I am not too totaly sure. Sorry I couldnt help you further.

Richard

[someone_4]

Hey Paul that was a very good question and you got me wondering .. =)
So I went on and posted your question. Here is the link.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x1ed85a3e6e0bd6118ff40090279cd0f9,00.html

Richard