Nesting Condition: Checks A Cell Containing An Email Address

I'm using excel 2000

I have a formula that checks a cell containing an email address, and if the format is not the office standard, displays a message. We now allow 2 variations, and I want to check for the second condition as well.

Basically, the email address is in the format

"Firstname"."Lastname@here.com

and the formula just checks the address against a lookup of names, the only seperator being period.

I now also need to be able to check for an underscore, and I don't know how to combine the conditions.

The existing forumula is

=IF((LEFT(A2,FIND(".",A2)-1))(LEFT(E3,FIND(" ",E3)-1)),"Check Email Recipient Main Database page column BQ:BR","")

and of course the underscore is easy, too

=IF((LEFT(A3,FIND("_",A3)-1))(LEFT(E3,FIND(" ",E3)-1)),"Check Email Recipient Main Database page column BQ:BR","")

but when I try to combine them, I get an error, or at best a VALUE output.

I think I need to nest them, but maybe there is a way to combine the conditions in or use "OR" and still get the "check email" message" ??