Messages Going Straight Deleted Folder

[Westwards]

From time to time I get an e-mail that seems to go straight to the the Deleted folder rather than my Inbox. I've looked to see if I can identify a pattern and it seems that his this some form of spam control that diverts e-mails with a long list of recipients. While I can see why could be desirable unfortunately I have missed a few important messages. My guess is that there is some way to turn off this filter, or at least adjust its behaviour, but I can't find it. Anyone know how this works?