I have gone through a lot of documents like RFC 822 and RFC 5322 and lot of Regex examples for email field.
All of them allow the single word TLD.For eg
test@test.c is valid ,but TLD 'c' ,is it even allowed for TLD's ?
.com , .in , .uk etc is OK but I have never seen a single letter TLD , so why is it allowed in all RFC's ?