Cannot recieve external emails

We have a network of around 30 people, they can all send and recieve emails internally, they can also send emails externally but cant recieve external emails..

any help would be great!
MIKEDUNN1878Asked:
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oldhammbcCommented:
are your MX records setup correctly on your domain so email comes though to your incoming mail server??
Alan HardistyCo-OwnerCommented:
Is port 25 open on your firewall inbound and is the firewall forwarding port 25 to your Exchange Server?

As mentioned above - check your MX records on www.mxtoolbox.com and make sure they are pointing to the right IP Address.
Mino DCCommented:
Do You have created the rule to your firewall / router so that the internal IP address of your SMTP server is published externally with a public address (NAT Rule).

The public DNS for your domain SMTP was created, and is it correct?
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MIKEDUNN1878Author Commented:
yes they are both ok, sorry i should of said, we have had no problems for a few years.. its not a new network.. this just happened yesterday.. I dont know if you heard about the BT meltdown yesterday.. it hit us and once the internet came back up here we could no longer recieve emails which seems odd??
oldhammbcCommented:
do you have a fixed external IP address? Im wondering if after the BT issues they have given you a different external IP address?? Can you try going to https://www.testexchangeconnectivity.com/ and doing the email test at the bottom? it should give you some info about weather the server can connect to your email server etc.

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Alan HardistyCo-OwnerCommented:
Check the Authentication Settings on the SMTP Virtual Server and make sure you have Anonymous Authentication enabled.  This kills inbound traffic very quickly if not enabled.
Alan HardistyCo-OwnerCommented:
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