There is no particular limitation: Linode does not provide a smarthost/mail relay service, so e-mail is entirely between your mail server and the recipient's mail server.
If possible, it would be a good idea to slowly ramp up the amount of e-mail traffic leaving your Linode's IP. This isn't due to Linode policy, but rather because receiving mail servers tend to "distrust" new IP addresses, particularly ones that suddenly start issuing a lot of e-mail. It usually works itself out automatically over a few days/weeks (except for Hotmail, of course), but that's a lot of mail landing in a lot of Spam folders until then...
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Code:
/* TODO: need to add signature to posts */