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I have postfix setup on my server so that I can send outgoing mail using the command-line:

mail -s "Subject" address@example.com

Is this using sendmail or postfix? Is "sendmail" just a software category or a distinct program? If something is "sendmail-ready" does that mean it will work with postfix?

Everything I've read online seems to use these two terms interchangeably.

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2 Answers 2

up vote 13 down vote accepted

Sendmail is a different (and much older) program from Postfix. However for every mail server to succeed in the Unix environment, a sendmail binary (with some of the expected command line options) must be provided.

EDIT: See for example the manual page for the sendmail program provided by Postfix

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In another words, Postfix emulates Sendmail. –  stepancheg Mar 7 '11 at 17:24
No it does not. It uses its own configuration files and does not understand sendmail.cf. –  adamo Mar 7 '11 at 17:30
Postfix does emulate Sendmail's implementation of sendmail, the message submission program. Other than that, they serve the same purpose, but accomplish it by rather different means. –  Novelocrat Mar 7 '11 at 17:45
Ok, so I can use most things that talk about requiring "sendmail" even though I have postfix setup because postfix has a mock-sendmail frontend script that handles everything. So my apps will never know it's not sendmail they are talking with. –  Xeoncross Mar 7 '11 at 17:57

Sendmail and Postfix are indeed both Mail Transfer Agents (MTAs).

Postfix is quite a bit easier for a new admin to set up, and has some nice features that integrate well with the mail store end of the process (Cyrus POP/IMAP, Dovecot, etc.).

If you're not actually going to be accepting email incoming into that box and it's getting forwarded to another system, something lighter such as Exim may be a better choice.

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I would love to setup Exim if it is noticeably smaller - but there just isn't that much out there on it unless you already know what your doing. –  Xeoncross Mar 7 '11 at 23:03
We use Exim on the forwarding boxes because that's what Ubuntu installs by default with mailutils. Running dpkg-reconfigure exim4-config and 30 seconds of configuration work to point it at the mail server. –  Magellan Mar 10 '11 at 17:48

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