I've found an increasing number of sites use validation preventing the use of '+' in email addresses (which I used extensively when on Gmail). To get around this, I use a feature of Fastmail to give me something similar - <myname>@<company>.<my.domain>. By putting the unique part in the domain, it's less likely to be stopped by a fussy validator. Combine with some of their auto-filtering and I have an easy way to track who's abusing their ability to mail me, and to take action appropriately.