sendmail and qmail are both message transfer agents (MTAs) for e-mail. However, they differ significantly in many respects. sendmail is more than 10 years old, qmail is currently (1997-05-22) available as version 1.01. qmail is designed to address the shortcomings of sendmail. These are (according to the author of qmail, D.J. Bernstein):
So what are the advantages of sendmail at all? sendmail isn't just an MTA, it implements a general purpose internetwork mail routing facility under the UNIX(R) operating system. (quoted from SENDMAIL: INSTALLATION AND OPERATION GUIDE ). If you don't need these features, then you are probably better off with qmail. If you need to do special header rewriting, mail routing, or something similar, you probably should use sendmail.
Here are some examples what can't be done easily with qmail. They are possible, but they require either some hacking by yourself, or the use of programs, which are written by others and have comments like: Ugly hack :-( I wouldn't want to rely on these (sorry, but I read the code, and it neither performs much error checking nor treats all possible cases).
SUBDOMAINis from a list we maintain (of our "customers"). This could be done in two ways:
SUBDOMAIN.uni-kiel.dewithout rewriting addresses. However,
smtproutesin qmail doesn't work with domains just having MX records, it wants hosts which have an A record. Of course we don't have the time to keep track of those.
virtualdomainsto strip off the
.d400. But you need to write that code yourself. I did this, but then I noticed that I can't route the rest of
.d400.deto our X.400 - SMTP gateway .
smtproutesseems to take precedence over virtual domains, so all mail got routed to the gateway.
qfw(written by Emanuele Pucciarelli ). However, as mentioned before, this is an Ugly hack :-( (cited from the code itself!).
qmail has also some other drawbacks. It doesn't adhere to some standards, e.g., it doesn't support DSN since the author simply says: DSN is obsolete. qmail's VERPs handle the same applications but, unlike DSN, don't require support from other hosts.
Another topic were qmail doesn't agree with standards is the support of 7bit systems. It simply sends 8bit all the time. If the other side doesn't handle that, you've lost. That is, you have to do it on your own, don't expect support from qmail.
If you have comments, corrections, etc, just let me know.