Why i can't use gmail account on a php email forum?

Question

Guys, can someone explain why i can't use a gmail account on php forums for contact page in websites?
I should use just bought email address?

Answer 1

do you mean a specific forum or do you ask in general?

Answer 2

I have no problems with my gmail account. never experienced any trouble...
must be something with the pages you visit. try asking the authors of the pages.

Answer 3

general

Answer 4

like when u make a contact page for a website...
there the client can write u a message directly, why i can't use gmail account for destination?