>>Having fought this problem, in this shape or other, since 2000, I'm simply stating that the client has to have their own mail server, period. The identity of the sender has to be the client, even if it's automatedservice@myclient.info - no buts and no ifs.
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>You can do that with Gmail (or any other mail service) as long as you have the right SPF configuration in DNS. I send email all the time for my west-wind.com account through gmail.
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>The biggest problem with GMail et al is that they do not allow bulk sending - if you send more than a few emails all at once or even within some interval, you'll get blocked.

Did that when I worked with a team who didn't have SMTP server, just an email branch of some CRM package, so I sent my mails via Google, to keep things separated from my private email. Since this was well within the limitations - I write far more code than emails - it was fine.

For business stuff I don't like relying on free services - there's always a price tag to them :).