Re: more on starttls, gnutls-cli and using tls for mail

[Tim Cross <theophilusx@gmail.com>]

On Sun, Aug 14, 2011 at 10:02 PM, Vijay Lakshminarayanan
<laksvij@gmail.com> wrote:
> Karl Fogel <kfogel@red-bean.com> writes:
>
>> Leo <sdl.web@gmail.com> writes:
>>>I use smtpmail-auth-credentials to pass different user names for the
>>>gmail smtps I am using. With the new smtpmail.el I haven't found a way
>>>to do that.
>>
>> Yes, I'm in that situation too now -- which is why I think it's so
>> unfortunate that `smtpmail-auth-credentials' went away :-(.
>>
>> I've found a way to do it, using the new smtpmail.el, but it's ugly.
>> I have `message-send-hook' set up ~/.authinfo for every mail message,
>> and then I remove the file afterwards in `message-sent-hook'.  Search
>> for "kf-set-up-authinfo" in [1] if you want the code.
>>
>> Naturally I hope we'll restore the lost functionality to smtpmail.el, so
>> this kluge will become unnecessary!  The ideal behavior, I think, would
>> be to pay attention to ~/.authinfo when it is present, but fall back to
>> trying `smtpmail-auth-credentials' when it's not.
>
> I have multiple GMail accounts and I use a hook to use the correct
> authentication depending upon which account I'm using.
>
> The hook function is
>
> (defun change-smtp ()
>  "Change the SMTP server according to the current from line."
>  (save-excursion
>    (let* ((username-fn
>            (lambda (from)
>              (when (string-match "\\<\\([A-Za-z.]*\\)@" from)
>                (setq from (match-string 1 from))
>                ;; Gmail addresses can have dots in them, so sending
>                ;; an email to abcd@gmail.com or a.b.c.d@gmail.com
>                ;; will go to the same destination.  So credentials
>                ;; for both addresses are stored under the symbol
>                ;; `abcd'.
>                (setq from (replace-regexp-in-string "\\." "" from))
>                (intern from))))
>           (from (save-restriction
>                   (message-narrow-to-headers)
>                   (message-fetch-field "from")))
>           (username (funcall username-fn from))
>           (credentials (cdr (assoc username *gmail-auth-credentials*))))
>      (if credentials
>          (setq smtpmail-starttls-credentials credentials
>                smtpmail-auth-credentials credentials)
>        (error "Could not find auth credentials for %s" from)))))
>
> (add-hook 'message-send-hook 'change-smtp)
>
> where the variable *gmail-auth-credentials* maintains all my user
> account info as an alist in the form:
>
> ((account1 ("smtp.gmail.com" 587 "account1@gmail.com"  "password1"))
>  (account2 ("smtp.gmail.com" 587 "account2@gmail.com"  "password2"))
>  (account3 ("smtp.gmail.com" 587 "account3@gmail.com"  "password3"))
>  (account4 ("smtp.gmail.com" 587 "acc.ount4@gmail.com" "password4")))
>
> I save it in a file ~/.gmails.gpg and in my .gnus I have
>
> (eval-when-compile
>  (load "~/.gmails.gpg"))
>
> Takes care of authentication.  Of course, now that this is out, someone
> could possibly get my email account information by convincing me to
> download their cool emacs package.  But I don't think I'm that important :-)
>
> Hope this code helps someone.  As with other Free Software licenses,
> this comes with NO WARRANTY.
>
>> -Karl
>>

You might be able to clarify something for me. Your the second person
I've come across in as many months who changes smtp server based on
the from address. Your process is even more of puzzling and I'd like
to understand what the reasons are.

For example, if your already authenticated with gmail's smtp server,
why re-authenticate with different credentials just to send a message
with a different from/return address? As far as Iknow, this is not
required and it seems to be adding a lot more complexity for no
apparent reason that I am aware of.

Is there any technical reason that requires this? I frequently use
authenticated smtp, but just auithenticate as one user and send email
with from/return addresses of different users with no problems.

I'm interested  knowing what the use case is for doing this as it
seems unnecessary and something which is making things needlessly
complicated. If there is a good technical reason to do it, I would
like to know so that I can be prepared should I need to modify my
setup and because I sometimes assist in maintaining a mail client and
like to be familiar with the various use cases.

thanks,

Tim