Postfix and MySQL, why?

[mariourk]

I know it is possible to combine Postfix with a MySQL database. Only I don't see why this is so much better that the standard maildir approach.

Our mailserver will be replaced by a new one in the near future. So this would be a good moment to see if anything can be improved. Right now we've always worked with mailboxes and that always worked fine. However, if there is a good reason to use MySQL instead, I would really like to know.

Hopefully someone can fill me in here
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If there is one thing to learn from history, it's that we usualy don't learn anything from it, at all.

[alex.blackbit]

all mail and groupware systems that are designed for large environments use databases as storage backend, m$ exchange, lotus domino, ...
this has several (possible) advantages

• speed (accessing a database is cheaper than performing open/close operations on ordinary files)
  
• easy replication (databases are designed to mirror the content redundant in different places, at least with one read only copy, which results in rebustness
  
• standardized data access path (SQL), in case you want to access the mails with custom applications for whatever reason (e.g. archiving)
  
• the known database advantages (e.g. ACID (well, that does not apply to all mysql storage backends))

you may or may not profit from using a database, but generally it is not a bad idea.
if you have the choice, favor postgresql over mysql.

[mariourk]

And are all the emails stored in the database as well? Or are the emails still stored in the maildir and is the database merely containing links (or an index, if you wil) to those files?
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If there is one thing to learn from history, it's that we usualy don't learn anything from it, at all.

[overkll]

Most users who implement postfix with MySQL use MySQL to store user/authentication information ie username/password/domain information. This way users aren't actually system users (user/password not in /etc/passwd) and cannot access the mail server via shell/login/ssh/telnet etc. The MySQL database IS NOT used to store email messages. Where and how messages are stored depends on you. One can use mbox files, maildir, or maildir like storage systems (like cyrus-imapd). Commonly used MDAs (mail delivery agent) are dovecot, courier-imap and cyrus-imapd.

MySQL can also be used for postfix access/lookup lists - mydestination, local_recipient_maps, aliases_maps, virtual_alias_maps, virtual_mailbox_domains, etc.

It's all very well documented at www.postfix.org

[mariourk]

But if emails are not stored in the database and users are not system users (because they are created in the database) where are the emails being stored? Right now the are stored in their home-folder. But when they are no longer system-users, there is no homedir. So, where does it go?

Perhaps someone knows some good documentation that explains how it basically works? All I can find are howto's that tell how to set things up. They often forget to explain why one would want to use it in the first place and how the principle works
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If there is one thing to learn from history, it's that we usualy don't learn anything from it, at all.

[overkll]

It sounds like your coming from an environment where one app does everything - Exchange, Lotus Notes? Excuse me if I'm making the wrong assumption.

Using postfix is completely different. It's main purpose is as a SMTP server/MTA - Mail Tranport Agent - routing incoming messages to a mail store or Mail Delivery Agent, and routing outgoing messages to their final destination on the net. Basically it's just relaying messages.

Postfix can be configured to deliver inbound messages to a mbox or maildir format mail store, AND postfix can be configured to deliver to an MDA (cyrus, dovecot, uw-imap/pop, courier, etc). The MDA is used to take care of the mail store, and connect users via pop/imap to their message store (INBOX and/or folders).

For example, I prefer a postfix/cyrus-imapd setup. Users are virtual users and are stored in a MySQL database. Both Postfix and Cyrus use the database for authentication. Incoming messages are received by postfix, then handed off to cyrus (the MDA) via lmtp. Cyrus will then store the messages in /var/spool/imap/. When users access their mail via pop or imap, cyrus (not postfix) controls the process of the users accessing/downloading their mail.

Where the mail is actually stored depends on the MDA, whether users are virtual or real, and how one configures it.

http://en.wikipedia.org/wiki/Mail_server

is a good place to start. Check the "See also" links as well

[mariourk]

Right now I'm using Postfix/Courier to handle the mail, so I'm familiar with what you are saying.
I just never realized that Courier would handle the storage of the mail and not Postfix. Actually,
this makes a lot of sense.

Your explanation helped me a lot, thanks!
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If there is one thing to learn from history, it's that we usualy don't learn anything from it, at all.

[alex.blackbit]

of course you do not have to, but if you wish to store the emails in a database too, you can use net-mail/dbmail.

[overkll]