on 2/7/2008 4:22 AM mouss spake the following:
Luke Dudney wrote:
There are lightweight SMTP clients that can be used as drop-in sendmail(1) replacements by speaking directly to a remote SMTP server instead of dropping the message in the local queue directory. One that I've used is mini_sendmail (http://www.acme.com/software/mini_sendmail/), though this was a while ago but I seem to recall having some success with it.
Others have mentioned the trade-off between the additional complexity of maintaining an MTA on each system and the fault-tolerance such a setup provides, however, you can achieve similar levels of fault tolerance by implementing redundancy on your relay server system(s). I guess it's up to you to figure out what's appropriate to your environment.
it's not a redundancy issue. it's a queue issue. when cron sends mail and if the sendmail command fails, cron can't do anything (it won't queue mail and retry later).
That said, one can write a script (perl comes to mind) or program that:
- replaces sendmail
- tries to send, and if it fails saves the message in a queue
- runs periodically (from cron for example) to check the queue
but I am not convinced that setting this up on every machine would be easier than configuring postfix or sendmail as a "null client".
Sendmail in its default setup is almost perfect in this respect. It doesn't listen to anything but localhost, and it will get security upgrades with the rest of the system. The only real change it needs is to set up a smarthost for it to relay its notices to, and an alias to root to receive the notices.
The default install of postfix might also be setup this way, but I can't vouch for that personally.