Are single quotes legal in the name part of an email address?

Question

For example:

jon.o\'conner@example.com ?

Answer 1

Although the answer is correct according to RFC 5322 the practice of using the quote (') has holes. Since it is string delimiter, too many automation and integration services fail when this character is used.

You will note that professional mail services like GMail do not allow it.

Strongly suggest that you use the alternate quote (`) if you need it, but in practice it should be avoided.