I have 2 edge servers running in my Exchange 2007 environment. For last few months I have problems with emails delivery from outside. I can see all emails in the queue but they are stuck there for some time. Sometimes it is few hours. So I have to wait and than all emails from the queue are delivered at once or I have to restart edge server and after restart they are delivered.
I just want to mention that sometimes it works normally and emails are delivered right away.