Reasons behind defaulting atd and sendmail

[Timothy Murphy]

Patrick O'Callaghan wrote:

> Kmail, Evolution etc. are MUAs (Mail User Agents). They also happen to
> work as simple MTAs because they can talk SMTP, but their primary focus
> is on the user, not the mail transport. Thus they don't use SMTP to
> receive mail, just to send it (see below), and aren't considered daemons
> in the usual sense.
> 
> Sendmail, Postfix etc. have no user interface to speak of and are
> focussed on queue management, security, efficient transport of large
> quantities of mail for many users etc.
> 
>> What about receiving email - don't I have to run rmail or equivalent?
> 
> The MUAs receive mail by a variety of methods, the most popular being
> IMAP and POP. In this sense they aren't acting as MTAs but as windows
> into a mail store maintained elsewhere, i.e. where an SMTP service is
> being run by some MTA daemon.
> 
> The original model of MTS/MUA (MTS is Mail Transfer Service, meaning
> roughly the collection of interconnected MTAs on the Internet) assumed
> that the user would have a local MTA depositing mail in a local store to
> be picked up by his MUA. POP and IMAP were invented in recognition of
> the fact that many users aren't going to run a full MTA and that the
> "store" is not local but exists on a remote server.

Thank you very much,
you have clarified the issues for me very well.

To return to the OPs desire for the sendmail service not to run,
it seems to me that there are three scenarios where this might make sense.

The first is a multi-user system running Linux on many computers,
as eg in a college or business.
In this case I would assume there was some system like kickstart
for installing Fedora or whatever on different machines.
In that case it should be easy enough to ensure that sendmail did not run,
if that is what is desired.

The second scenario, which I imagine is becoming more prevalent,
would be a home system with a server serving a number of laptops.
It is my impression that there are a number of places
where email is used in such a case to communicate between the machines.
I'm not sure if sendmail is normally used in these cases.

The third case is there there is a single machine
collecting email by POP or IMAP and sending email by "direct SMTP",
as you have explained.
I guess in this case it makes sense to turn off sendmail,
though on the other hand I can't see any harm in leaving it running.






-- 
Timothy Murphy  
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland