[joezydeco]

"If you sign up for some website that requires an email address (especially if they might spam), using a + alias lets you create a filter for the stuff they send"

It's a great idea...but I'm encountering more and more sites that reject your email address outright if a + is in there anywhere.

[breakingcups]

If this happens to you, you can also use the period sign with GMail. So [e-mail] also receives email addressed to [e-mail] [e-mail], [e-mail], etc.

[ses4j]

Do you think they're intentionally blacklisting the +, or are they just writing sloppy validation/regexes that aren't up to the spec?

[joezydeco]

Hard to say.

I've encountered it on some very large and famous websites, so I'm thinking it's not always the fault of a bad regex.