Exchange 2007 responding with 499 no file descriptor error

We have a problem receiving mail on our Exchange 2007 server.  Inbound mail is being rejected with the error:

2010-04-28 15:06:02 M=<D68E52DBA02FD34DA0CE008BAF05D35905DF37ED24@SVEXCHCLUSTER.m1.local> SZ=786704 C="499 no file descriptor"

When telnetting to the server we're getting messages like this:

Connected to
Escape character is '^]'.
220 *********************************************************************************************

I'm told the string of *'s is exchanges way of saying something is wrong.

Emails get through after a couple of hours.  We changed broadband supplier a couple of weeks ago. Nothing else has changed.  We use Symantec Mail Security for MS Exchange for anti spam and email virus scanning.
Who is Participating?
this is the reply of a PIX firewall

go to the PIX and disable SMTP checking it should work

Peter_CullAuthor Commented:
Great answer.  My ISP enabled SMTP checking without telling me.  They disabled it and now email is arriving fine. Cleared the backlog in minutes.  Many thanks.
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.