bug#45711: 27.1; Ambiguous account match in .authinfo still used by smtpmail

[Duncan Bayne]

Lars Ingebrigtsen writes:

> Duncan Bayne <duncan@bayne.id.au> writes:
>
>> What it seems to be doing with (car (... :max 1) is to simply take the
>> first match and use that.
>>
>> What I *think* it should do is either a) error out in the case of an
>> ambiguous match, or b) prompt the use to ask which of the various
>> matches it should use.
>
> As Ted said, it's common to have specific passwords for some services,
> and use a fallback for the rest.
>
> machine foo port smtp password zot
> machine foo port nntp password bar
> machine foo password gazonk
>
> Changing how this works would break people's setups, so we can't do
> that.

In the case you've cited above, there is no bug.  I wouldn't change that
behaviour at all.  There is only one SMTP account present.

But consider this hypothetical configuration (not so hypothetical,
because as I say, this recently happened to me):

machine foo port smtp login Alice@example.com password zot
machine foo port smtp login bob@example.com password bar

If smtpmail is configured not to specify smtpmail-smtp-user, *and* there
are multiple SMTP accounts in .authinfo, it'll just quietly use the
first account.

This behaviour I argue *is* a bug, because that is almost certainly the
wrong thing to do.

Perhaps to put it another way - can you imagine a case where it
*wouldn't* be a bug for smtpmail to behave in this way?  I honestly
can't.

> But I see that this hasn't actually been documented anywhere?  So
> I've now added that to the auth manual in Emacs 28.

Thank you :)  That would have been helpful at the time this was
initially confusing me, & will hopefully help others too.

--
Duncan Bayne
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