I'm truly not sure why knowing the company email address (domain) would matter.  Most of us have our own company domain names and email addresses that "AREN'T" gmail accounts?  We're company owners and administrative support personnel that have our own corporate (non-gmail) email addresses.

Example (removed that at sign so it can be seen):

invoicing AT companydomain.com

This issue with outgoing email is actually a big issue for most of us and it seems like is should be a simple fix in the grand scheme of things.  Bottom line is that we want our customers to receive emails/invoices from us not you?

KL