the only real difference between the registration email and the verification eamil is the from address setting.
in the WA_Globals/WA_Globals.php file, what is set for:
$WAGLOBAL_Registration_Email_FROM
and what is set for:
$WAGLOBAL_Verification_Email_FROM
also what about the registration subject versus verification subject?
we are investigating the issues with different browsers, however, with Fire Fox 5 being in beta testing stages, we probably wont investigate that one to much till it is released.