This was bugging me a little. I use Gmail as it links in nicely with my Android, and I like the calendar and and the fact that all my contacts are on there too, but my main email address not a Gmail account, although I have moved all my accounts into Gmail and they are all separately labelled. This is very handy when checking emails on a remote pc etc., I only have to login to one webmail account.
Anyway, after some testing, I found that in Outlook, emails I was sending from my other accounts were displaying with sent “on behalf of” my Gmail account. This looked naff, and I did’nt really want this displayed.
The fix was simple. In Gmail, go to Settings, and then Accounts and Import. See the Send email as section and then edit each of you other accounts. Click throught the process and the second screen will allow you to send via your original SMTP server rather than Google’s, sorted.