Sendmail applet may need to validate on RCPT

[Denys Vlasenko]

On Sunday 29 March 2009 19:24, Vladimir Dronnikov wrote:
> >> -am<meth> to specify login method
> >>
> >> http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html
> >
> > I think it's best to act compatibly with it.
> 
> Bad news :) For it's quirky and not busyboxy.

You do not need to implement all of it. You just need to make sure
that what yu do implement, works the same.

> >> And BB sendmail is mainly MUA; however, to be compatible it
> >> combines both MUA and MTA options.
> >
> > I don't understand MUA/MTA slang. I understand "SMTP client",
> > "SMTP server", "POP3 client", "POP3 server", same for IMAP.
> > Can you rephrase the above for dummies like me?
> 
> BB sendmail is not SMTP server; it is SMTP client (cause it talks to
> SMTP servers)

That much I understood.

> and is partially a user agent (since it composes mail 
> messages).

This does not seem to be that important a distinction (whether
it sends messages verbatim or processes them a bit).

> Vanilla sendmail, in contrary, can be run in both server 
> and client modes. To be compatible in option area BB sendmail has to
> accept both client and server options.

I don't see why do you want to accept server options.
This can only fool users (so it's worse than useless, it's harmful).
Better to bomb out if they try to run
us as a server, since we don't support that half of the sendmail.

> >> So I treat -a for attachment as quite common choice.
> >
> >> > * "vanilla sendmail"?
> >> > * other sendmail clones?
> >>
> >> They are MTAs, and have nothing to do with attachments.
> >
> > I don't understand.
> 
> None of sendmails (AFAIK) deal with attachments. They just feed its
> input to SMTP server. I found (and still find) that it is very useful
> to allow to specify attachments without use of additional utilities.
> That makes sendmail a solid peace of software.
>
> > In sendmail world, how do they send mail from command line?
> > IOW, what is their "SMTP client" program, and how does it
> > take attachments?
> 
> I just don't know. I didn't use standard utilities at all. My
> experience was to write a shell script (I called it mailer) which
> composes the mail message given subject, recipients, attachments and
> body. I then fed its output to XMail's sendmail helper, which is dumb
> enough to take only a couple of options.

This is ok *if* there is no popular program which does that already.
You can invent API yourself then.

If there is such utility, then mimic it.

> > I think there's need to add largish comment to sendmail.c and explain,
> > which clones of sendmail are popular in the wild, which options
> > they support, which options from those do _we_ support.
> > If we have aliases for sendmail applet (or will have, like "ssmtp"),
> > and have different options supported for each, that needs to be documented.
> 
> Good job.
> 
> > If this sounds boring to you, consider how much of confusion
> > that will clear up, and sendmail developers will have clearer
> > vision what we have now, and what we are trying to emulate.
> > Currently, it requires either telepathy or extensive knowledge
> > of Linux's command line mail utilities from various projects.
> 
> It indeed is boring. But who cares :)
> 
> I'm going to split sendmail into parts. This seems the only way to
> avoid option hell.

As I see it from googling, both sendmail and ssmtp accept
input from stdin. Then, you can split message creation
and message sending like this:

makemail -a ATTACH -b BODY -f FROM -t TO -c CC | sendmail/ssmpt ...

where makemail is either your own invention with your own API,
or a "compatible" clone of something existing already.
--
vda