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Anyone can tell me if me use postfix and dovecot but not have reverse dns set : i not will got mails? or not cant send? what will happen?
(((o(ﾟ▽ﾟ)o))) If privacy is outlawed, only outlaws will have privacy. (((o(ﾟ▽ﾟ)o)))
ヽ(`Д´)ﾉ Everyone should run Tor on their idle servers.
You can send email even without valid PTR record, but its deliverability will be bad. Most email servers will consider your messages as spam.
@miklos: no rDNS, no SPF setup and no DKIM signatures in outgoing mails = most will bounce or wind up in blackholes. Another words: don't bother, instead use solid third party service like mxroute, which will cost you less than your own MX anyway. This is assuming you are not looking to spam people, of course.
If you don't have rDNS set, it's up to the foreign domain to think you are not authentic from the domain you stated you are from, and most likely they will. Without MX record, mails from foreign domains have no idea which server to deliver the mails to.
rDNS and SPF are pretty much required these days. Don't expect recipient servers to accept mail otherwise. Most places like Gmail and Hotmail will reject it and even Postfix, itself, has an option to do reverse lookups and reject if not valid.
DKIM, in my experience, isn't required, but it's good to have and pretty easy to setup.