Some emails aren't arriving, but I can send email!

There have been reported issues of users not receiving emails, but are able to send emails out. This may be due to the Virus Blocker application scanning SMTP traffic, where the scan causes the traffic to take longer than the internal mail server's TTL value. As a test, uncheck the Scan SMTP option located in Apps > Virus Blocker > Scan Options. If this fixes the issue, then you will need to increase the TTL value on your internal mail server.