Mails are in queue suddenly not sending out are not working Exchange 2013

we have 2 Exchange 2013 servers which are DAG enabled and CU 10 updated

suddenly mails are not getting out of both the servers

both servers are able to browse internet
both servers are able to talk to each other
servers and services are restarted
ISP internet restarted as well

still mails are pending at the queue
Joe FrixonBusiness OwnerAsked:
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Joe FrixonConnect With a Mentor Business OwnerAuthor Commented:
the issue was at the ISP end. not sure what was the issue as internet was working for everyone in the office even on these two servers but still the mails were not going out.

however when the issue was reported to ISP and then after an hour it started working.

I presume the issue to be with DNS forwarding.

Thanks for all the support
Warwick ReimanConnect With a Mentor Senior Systems EngineerCommented:
Any Logs? is this an active//active dag with DAC? I had this issue the other day with a corrupted database and had to rebuilt it which cause mail to stop routing. Check to make sure edge transport is also working correctly.
Scott CConnect With a Mentor Senior Systems EnginerCommented:
Stop and restart the Transport Service to see if that gets things moving.

If it doesn't, the next question is "What recently changed?".

Something has to have changed.   A working Exchange server does not simply stop sending emails.

Are you able to receive emails?

Is your Cert still valid?

SMTP relay?  Check for any blacklisting.
Joe FrixonBusiness OwnerAuthor Commented:
the issue is beyond the local issue it was at the ISP end
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