Send mail errors messages NOQUEUE: Null connection

[David Johnson_6]

Hello evey one.

I get the following error messages every day.

Dec 22 01:46:37 ccchpl sendmail[3853]:NOQUEUE: Null connection from TC222-156-1-66.adsl.dynamic.apol.com.tw [222.156.1.66]

and this

Dec 23 03:34:36 ccchpl sendmail[19447]:DAA19447: lost input channel from[125.188.61.77]

I do not know what these errors mean.
Could someone please point me in the right direction.
Thank you.

[Steven E. Protter]

Shalom David,

Both errors mean that the connection to the communicating server was cut off for some reason. It could be due to a failure of networking anywhere between the two machines, it may be a firewall inserting a block IP address. Could be anything.

Both errors seem to indicate other servers having trouble submitting email to your server. The problem could simply be at the other end. There is therefore nothing to do about it.

If you are receiving normal mail volumes you may be able to ignore this error.

SEP

[Sameer_Nirmal · Accepted solution]

Hi,

>sendmail[3853]:NOQUEUE: Null connection >from TC222-156-1->66.adsl.dynamic.apol.com.tw [222.156.1.66]

What this actually means is that sendmail had started an smtp connection from "TC222-156-1->66.adsl.dynamic.apol.com.tw [222.156.1.66]" host. But the communication between them breaks because of network error ( DNS error, un-reachable host )Since conection is dropped, sendmail reports the above error as warning as there is no reply from the remote host within a defined time. The various timers are defined in the "sendmail.cf" file.

>sendmail[19447]:DAA19447: lost input >channel from[125.188.61.77]

When sendmail receives an SMTP connection from a remote host, and it loses its network connection during the communication,
above error would be reported.

You can check for any error using
# sendmail -v -d8.99

If sendmail hangs or errors ( timeout etc ), then there is network problem either at DNS server, remote SMTP server or at network layer level ( firewall etc ).

As per log given, it seems that these errors are apprearing for different host. You need to check the mail.log file for sequence of these errors for a particular host to know the whats happening exactly.

Check the network using ping, nslookup etc. and at sendmail level using above method.