ChapterÂ 5.Â Moving from Sendmail to Qmail
More often than not, a site that plans to run qmail is already running some other mail software on a Unix-ish server, and more often than not, that software is sendmail. This chapter walks through the steps involved in moving a mail system from sendmail to qmail.
Running Sendmail and Qmail in Parallel
Users tend to be upset when they canât access their email, so itâs rarely possible to shut down the old mail system, spend a day getting the new system installed and tested, then turn the mail back on. Fortunately, you donât have to. Itâs easy to run sendmail and qmail in parallel on the same machine, delivering mail into the same mailboxes, until youâre satisfied qmail is working properly, and then shut sendmail down.
Any MTA receives mail through two routes: local and remote. On Unix systems, local mail is injected via the sendmail program, and remote mail is injected via SMTP. When youâre running qmail and sendmail in parallel, as long as /usr/lib/sendmail is a link to sendmail, local mail will go to sendmail, and as long as sendmail is listening on port 25, remote mail will also go to sendmail. While youâre testing, put qmailâs version of sendmail somewhere else, say /var/qmail/bin/sendmail, and run qmailâs SMTP daemon on port 26.
Once youâre happy with your qmail installation, move the original /usr/lib/sendmail to /usr/lib/sendmail.old (and similarly for any other links to it such as /usr/sbin/sendmail) and link the ...
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