Postfix Performance Tuning
Postfix Performance TuningThe hints and tips in this document help you improve the performance of Postfix systems that already work. If your Postfix system is unable to receive or deliver mail, then you need to solve those problems first, using the DEBUG_README document as guidance.
For tuning external content filter performance, first read the respective information in the FILTER_README and SMTPD_PROXY_README documents. Then make sure to avoid latency in the content filter code. As much as possible avoid performing queries against external data sources with a high or highly variable delay. Your content filter will run with a small concurrency to avoid CPU/memory starvation, and imeta http-equiv="Content-Type" content="text/html; charset=us-ascii">
Postfix and UUCP Despite a serious lack of sex-appeal, email via UUCP over TCP is a practical option for sites without permanent Internet connections, and for sites without a fixed IP address. For first-hand information, see the following guides:
Local network <---> LAN to
UUCP
Gateway<--- UUCP ---> Internet
to UUCP
Gateway<---> Internet
And here's the table of contents of this document:
Here is how to set up a machine that sits on the Internet and that forwards mail to a LAN that is connected via UUCP. See the LAN to UUCP gateway section for the other side of the story.
You need an rmail program that extracts the sender address from mail that arrives via UUCP, and that feeds the mail into the Postfix sendmail command. Most UNIX systems come with an rmail utility. If you're in a pinch, try the one bundled with the Postfix source code in the auxiliary/rmail directory.
Define a pipe(8) based mail delivery transport for delivery via UUCP:
/etc/postfix/master.cf: uucp unix - n n - - pipe flags=F user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
This runs the uux command to place outgoing mail into the UUCP queue after replacing $nexthop by the next-hop hostname (the receiving UUCP host) and after replacing $recipient by the recipients. The pipe(8) delivery agent executes the uux command without assistance from the shell, so there are no problems with shell meta characters in command-line parameters.
Specify that mail for example.com, should be delivered via UUCP, to a host named uucp-host:
/etc/postfix/transport:
example.com uucp:uucp-host
.example.com uucp:uucp-host
See the transport(5) manual page for more details.
Execute the command "postmap /etc/postfix/transport" whenever you change the transport file.
Enable transport table lookups:
/etc/postfix/main.cf: transport_maps = hash:/etc/postfix/transport
Specify dbm instead of hash if your system uses dbm files instead of db files. To find out what map types Postfix supports, use the command "postconf -m".
Add example.com to the list of domains that your site is willing to relay mail for.
/etc/postfix/main.cf: relay_domains = example.com ...other relay domains...
See the relay_domains configuration parameter description for details.
Execute the command "postfix reload" to make the changes effective.
Here is how to relay mail from a LAN via UUCP to the Internet. See the Internet to UUCP gateway section for the other side of the story.
You need an rmail program that extracts the sender address from mail that arrives via UUCP, and that feeds the mail into the Postfix sendmail command. Most UNIX systems come with an rmail utility. If you're in a pinch, try the one bundled with the Postfix source code in the auxiliary/rmail directory.
Specify that all remote mail must be sent via the uucp mail transport to your UUCP gateway host, say, uucp-gateway:
/etc/postfix/main.cf: relayhost = uucp-gateway default_transport = uucp
Postfix 2.0 and later also allows the following more succinct form:
/etc/postfix/main.cf: default_transport = uucp:uucp-gateway
Define a pipe(8) based message delivery transport for mail delivery via UUCP:
/etc/postfix/master.cf: uucp unix - n n - - pipe flags=F user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
This runs the uux command to place outgoing mail into the UUCP queue. It substitutes the next-hop hostname (uucp-gateway, or whatever you specified) and the recipients before executing the command. The uux command is executed without assistance from the shell, so there are no problems with shell meta characters.
Execute the command "postfix reload" to make the changes effective.