Discussion on: Checking Mail Address Simply using Perl Regular Expression

How far down the regex rabbit hole do you want to go?
Must start with a letter/number
Can have one period before the @
Can't have more than one period
Cannot have spaces
Must be at least one letter/number between period and @
Must be at least one letter/number immediately after @
Must be a period after @
Must be at least two characters after the period
Can be a second period after the min 2 chars if they are co
Must be 2 chars after the the second period
They must match a list of country codes.