The host of the site I'm working on tends to shut off email if a certain number of fails take place. Needless to say this is a bit of a pain even if it's justified to fight spam. Is there a way to test if an email address has failed once so it can be flagged?
+1 For John Conde, but also you could think about switching to an host who won't penalize you for this kind of problem. I understand it is Ok to fight spam, but blocking an e-mail account for a paying customer may not be the best way to achieve this, there are tons of host who won't act like this, or you could think about getting a private mail server?