Mail 4/Gmail sync, sending mail problems

[saxaphony]

I have Gmail gathering the emails from my two email accounts--a personal gmail account and my work email from a business domain (that Gmail checks via POP3). I have set up my Mail app to sync with my Gmail account (IMAP) so that it receives mail from both accounts as well. I only added the Gmail account info to Mail since Gmail checks both accounts. The problem is when I use Mail to write emails, I can only send using my Gmail account. Is there a way to set up Mail so that I can send and reply from either my Gmail account or my work email and have these sent messages sync with Gmail as well? Is there a way to add another smtp so that I can choose to use either one?