Problems Recieving Mail From Domain

[thunder04]

Hey Guys,

We've suddenly started having problem receiving mail from one of our sister school districts. I'm trying to figure out if it's us or if it's them. All I can find in the log related to their domain are entries like this:

Apr 29 13:26:42 cottontail postfix/smtpd[23956]: connect from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 13:26:42 cottontail postfix/smtpd[23956]: lost connection after EHLO from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 13:26:42 cottontail postfix/smtpd[23956]: disconnect from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:07 cottontail postfix/smtpd[26091]: connect from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:07 cottontail postfix/smtpd[26091]: lost connection after EHLO from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:07 cottontail postfix/smtpd[26091]: disconnect from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:08 cottontail postfix/smtpd[20215]: connect from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:08 cottontail postfix/smtpd[20215]: lost connection after EHLO from le-m600.llesd.k12.ca.us[149.20.82.5]
Apr 29 14:30:08 cottontail postfix/smtpd[20215]: disconnect from le-m600.llesd.k12.ca.us[149.20.82.5]

Is there anywhere I can look that'll give me more details on how/why the connection was lost?

Any help would be much appreciated!

[thunder04]

If it helps any, their mail server reports

----- The following addresses had transient delivery errors -----

in the bounce their users recieve when sending us e-mail. We can't seem to get any more details from them other than that, unfortunately.

I'm not sure what "transient deliver errors" are!