[imp] Dynamic mailer config based on FROM and TO addresses

[Robin Bankhead]

Quoting Michael M Slusarz <slusarz at horde.org>:

> Quoting Robin Bankhead <horde at headbank.co.uk>:
>
>> Hello,
>>
>> I am hoping to use Horde/Imp (latest horde-webmail from PEAR) with  
>> Apache James v3 (eternal beta) as IMAP server and local delivery  
>> agent.  The local mailstore will be receiving mail from a number of  
>> domains/accounts, but it has no true FQDN of its own, so everything  
>> gets fetched into a single @localhost IMAP mailbox.  That IMAP  
>> login is set to autologin in horde main config, and Imp uses it via  
>> $servers['imap']['hordeauth'] = 'full'.
>>
>> The James SMTP server *could* relay all outgoing mail for all these  
>> domains, but in my testing this has garnered high spam scores, even  
>> when clients are locally doing SMTP AUTH.  I guess this is because  
>> of our lack of an originating FQDN.
>>
>> I'd therefore like to have Imp choose the SMTP server config  
>> dynamically upon sending, based on both From: and To: addresses of  
>> the outgoing message.  The user would choose the From: address  
>> using a list of Identities defined in global prefs.  The
>>
>> The things I need to know are:
>>
>> 1. Can this be implemented at all? (I reckon it can, but...)
>
> Sure.  But you will have to directly change the source.
>
>> 2. Would I implement it by a routine in one of the conf files (I  
>> have done it like this before, for turba config circa H4) or would  
>> I need to use a Hook?
>
> No.
>
>> 3. Where do I find the variables I need for
>> (a) The From: address or Identity, and
>> (b) the To: address?
>
> Just grab them from the code.  You want to look at the  
> IMP_Compose#sendMessage() method (imp/lib/Compose.php).   
> $GLOBALS['injector']->getInstance('IMP_Mail') returns the mail  
> transport object - you will need to replace that with whatever code  
> you need to create the proper mailer object needed based on the  
> addresses.
>
> michael
>

Thanks Michael, this saved me a lot of misdirected effort.  If I may,  
a couple of follow-ups:

1. The "cleanest" way to attack this (least disruption to existing  
core code) seems like it would be to make a child to the  
Horde_Mail_Transport_Smtp class.  Is that extra level of inheritance  
likely to break anything else, that you know of?

2. Would invoking by default this putative child class (call it  
Horde_Mail_Transport_Smtpcustom) be simply a matter of declaring  
$conf['mailer']['type'] = 'smtpcustom' ?  The idea being I'd then not  
need to alter IMP_Compose::sendMessage().

3. In one scenario (mixed local and external recipients) I'd need to  
effectively split the message into two when sending (one for each  
category of recipients, going to their respective mailers).  At first  
blush it seems like I could do this within my Smtpcustom class; do you  
agree, or would it
  (a) be offensively improper conduct, and/or
  (b) break things all over the place?
(I notice that IMP_Compose::buildAndSendMessage() is where this  
splitting happens for S/MIME multi-recipient messages, so I could  
probably do something there but it'd mean making my code additions  
less self-contained.)

Best,
Robin Bankhead