Share this one with your IT guys & gals.
We have had several calls over teh past month or so where recent updates to a site's firwalls have resulted in emial issues. Some emails are a reuslt of a Task being issued User to User within the system. For that type of task the Creator name is inserted as sender. When the Recipient, is atteh same domain as the Creator, it is likely that the spam filters try to match the email server domain from the sender line with teh originating email server domain, finds a mis-match and blocks the email.
Not all emails coming from Tasks have this same situation so the issue may appear intermittent.
The fix is to have IT , make < mail.pbtg.com > a trusted site.