Exchange 2013 Intermittent EMail delivery and OWA connection.

[Archipelego1]

Since Wednesday, we have been having problems with receiving and delivering email. We find that emails will stick in the exchange queue for hours, before wirking through and being delivered.

 

We've also noticed that whenever emails aren't delivered, we're also not able to access the OWA website externality... Although we can can access internally. When we're unable to access OWA, I can still ping our external IP address.

 

Does anyone have any ideas what the problem could be?

 

Nothing was changed prior to the problem. We have a smoothwall firewall and virgin internet connection.