It seems there is too short a limit on trusted sender email addresses for me to trust Twitter's sending addresses. Because Twitter encodes the intended address (which is a spamgourmet address) in the sending address, presumably to detect bounces usefully, it comes out as:
twitter-dm-XXXXXX.20.XXXXXX=spamgourmet ... witter.com
(Where XXXXXX.20.XXXXXX is the @spamgourmet.com address I used to register with Twitter.)
I'm sure the 50 char limit has something to do with "it should be plenty" and also something to do with database size and indexing efficiency. I understand if it just isn't possible to increase the limit. To deal with the Twitter sender addresses, however, I need at least 73 characters.[/u]