It has been 6 years since I worked at the US Dept. Of Justice and had the RFCs memorized
but you can see that others agree with me. Neither Email::Valid
believe 'foo.@bar.com' is a valid email address and Email::Valid::Loose
only exists to relax the rules of RFC 2822 to allow a period before the at.
Regarding case sensitivity in the user portion, you did make your position clear. In fact, I indicated you had already mentioned it. I brought it up again because I believe it would be a valuable rule to turn on/off if they were using this theoretical module to identify spammers.
The reason I suggest such a pick and choose module is thus: The specific reasons for wanting to look for email addresses and then choose to deem them invalid changes from situation to situation. Most folks are completely ignorant of the RFCs and it would be easy for them to say "in my situation, I want to allow X and Y but deny Z" without having to go look anything up.