> According to sendmail doc, only if .procmailrc file exists will sendmail
> deliver to procmail. I don't have any .procmailrc files, so I assume
> procmail is not used. However, even if it was used, then as there are
> no recipies to catch any emails, then they will all go to the default
> spool file anyway.
In any way there must be an LDA configured in sendmail.mc. By default on
Redhat and Fedora systems that is Procmail. It can be a different
program as well, like Maildrop or the Cyrus deliver. Again, Sendmail
does not store any message itself. That does the LDA (local delivery
agent).
If you use no /etc/procmailrc or ~.procmailrc then you use no filtering,
sorting or whatever is possible using Procmail. but Procmail is invoked
to store the message in the mail spool.
> So the point is that all mail goes into a file:/var/spool/mail/USER
Right.
> I am only talking about 1 machine, my server.
> It runs sendmail... which delivers incoming emails to local disk file
> /var/spool/mail/USER.
> I am asking about a local user, who uses Kmail to access the same
> local disk file:/var/spool/mail/USER on the same machine.
> My understanding (expectation) is that if I have 2 applications reading
> and writing to the same file on the same machine (same fs/disk), then
> they should use some locking system - to stop them both accessing it
> at the same time.
That is correct and the case.
> OK, only sendmail is writing to the file, but Kmail will remove it - so
we
> should avoid conflicts ?
Procmail is writing and Kmail want to have full access, ok.
> So I hope that is a clear explanation of why I am asking:
>
> What locking method should I use ?
I can't say how Kmail works. It should handle that case proper as long
as there is a setup option to get the user's mail by accessing the mbox.
You should not care about anything with that.
> If the answer really is 'none', I'd be very surprised - but I'll trust
your
> answer if thats the case.
You would only have to care if you intend to write your own mail client
;)
> I don't see how IMAP/POP are relevent in my situation - its all on a
local
> fs/disk, so I don't think I'm running IMAP or POP (don't even know what
> IMAP is).
Even if you receive the mail by Sendmail on the same machine where you
use Kmail you can use an IMAP/POP3 server. I just suggested that as it
sounded to me as if you would get errors when using Kmail. Something
like "cannot access because the file is locked". Then I would guess
Kmail does not handle the situation proper and you should switch to an
IMAP/POP3 server and setup Kmail to no access the mbox file but the
IMAP/POP3 server.
> If I want to read mail from an outside source, I'll use (and have done)
POP,
> and that works fine.
Ok, you could do that on the same machine as well.