Running Exchange2007, internal mail is fine but not recieving any mail from outside sources

We are running Exchange 2007 and all of a sudden, users cannot recieve email generated from outside the network. Email internally and email outbound to another destination works fine. As far as I can determine, senders are not getting any NDR's as a result of the email not arriving.
SynergonAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Antonio VargasMicrosoft Senior Cloud ConsultantCommented:
First you need to specify your infraestructure. Is port 25 opened on your firewall allowing the mail to come in? Is the mail reaching exchange? if it worked before and it's not working now, without any changes, probably mail is not reaching exchange and you need to understand why. Your firewall must be allowing port 25 traffic in and must be tranlating the entry. You probably need to say that everything that comes from port 25 to your external ip x.x.x.x goes to port 25 on your internal ip x.x.x.x.
is it going directly to exchange or do you have a mail relay and filter system?
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Email Protocols

From novice to tech pro — start learning today.

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.