Re: Mail plugins for modifying headers on outgoing messages

FROM : Dave Camp
DATE : Thu Nov 18 18:54:28 2004

Do you have to do HashCash as a part of Mail, or could you implement 
some sort of local SMTP relay app that could do it for you? That would 
give you full control over the mail and let you display whatever UI you 
needed.

Dave

On Nov 17, 2004, at 9:18 PM, Wade Tregaskis wrote:

> I'm writing a Mail plugin to add Hashcash support, and while it's 
> pretty easy to read immutable messages at various places, and there's 
> suitable notifications to catch for doing so, there appears to be no 
> "ideal" way to slide some code into the sending process.  GPGMail 
> takes a very verbose approach with replacing controllers and nasty 
> such hacks, which is fine for their use where they use other 
> functionality derived from that, but seems like major overkill for 
> what I want.  Additionally, it would be better to calculate the 
> Hashcash stamps when messages are actually sent (not just queued or 
> placed in the Outbox).
>
> So, knowing all this and after a few hours of playful hacking, I've 
> found at least "an" approach is to pose as MailDelivery and override 
> the headersForDelivery method.  I at first tried modifying the 
> OutgoingMessage class (and related), but for some strange reason any 
> changes you make to these have no actual effect - it seems they're 
> created redundantly, or at least doing something obscure and tricky. 
> I can't figure out what the real class is for outgoing messages, thus 
> the MailDelivery approach, which I feel is less elegant, but does 
> actually work (as evident by the X-Hashcash in this email's headers).
>
> Anyway, the point I'm getting at is, is this the best way to do what I 
> want?  I know posing as MailDelivery is generally a bad thing, but 
> there seems to be no other way to do it - Mail isn't of course really 
> designed with plugins in mind, and while interface stuff is easy 
> enough to modify, the guts of it are almost air-tight to the outside 
> world.
>
> A problem with the approach I've taken is that it's entirely 
> non-interactive... I can probably post activity messages, but that's 
> about it, I imagine.  Not without some really icky hacking about, 
> anyway.  In my use as it stands this shouldn't really be a problem, 
> but I've an eye for the future...
>
> Wade Tregaskis (AIM, Yahoo & Skype: wadetregaskis, ICQ: 40056898, MSN 
> & email: <email_removed>, Jabber: 
> <email_removed>)
> -- Sed quis custodiet ipsos custodes?
>
> P.S.  Yes yes, people who add plugins to Mail will be hexed into the 
> next life, I know. :P
>
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