Question : Sendmail stat=Data format error

Hello,
I'm having some very strange problems with Sendmail.  We have a BSD box that runs our network monitoring software.  The software is configured to send text messages to our cell phones when there is a problem.  A guy that managed this server recently left the company and I think he made some changes before he left that broke Sendmail.  We used to get messages on our phones but we don’t anymore.  When I checked the maillog I see the following errors:

Jan 19 11:24:54 mail sm-mta[520]: k0JGOrqQ000518: to=<[email protected]ngular.com>, ctladdr=ain.com> (1008/1008), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=30385, relay=mx.mycingular.net. [66.102.172.222], dsn=5.6.0, stat=Data format error

Obviously 1112223333 is not a valid phone number.  I just put that in there.  Same with ourdomain.com.  To rule out problems with the monitoring application I tried sending a message to my phone using the mail command.  It fails with the same error.

I researched the stat=Data format error trying to find out what it meant.  From what I found people relate this error to a DNS problem that can be fixed by adding an entry to the /etc/hosts file.  Our host file is correct and hasn’t been edited in a long time.  I checked the dates on the files in the /etc/mail directory and also for our monitoring program but I can’t find anything that was edited recently.  The monitoring program is Nagios

We were able to send messages to our phones before but now it doesn’t work.  I’m stuck from a troubleshooting perspective and want to get some advice from the Experts on this site.  Anyone have any ideas what might be causing this error or give me some troubleshooting steps?

Thanks for the help!

Answer : Sendmail stat=Data format error

It's possible that cingular changed their servers to be more strict. Make sure your server has reverse dns for the public ip it sends mail from and make sure it uses a valid fully qualified hostname in the helo command (not an ip or random stuff). To test this send and email from this server to some mailbox (on a different system) you have access to (gmail,hotmail) something like that and look at the headers. If you aren't sure what to look for post the headers here.