> Ideal would be if
> 1) every posting here (for the main topics I sign up for) also
> got sent to me.
I think that can be arranged, as explained in a previous posting. At least with Smartfeed, everything will go into the feed. That seems to work for me with Thunderbird.
> 2) every posting got sent to an email list (email@example.com
> that people could subscribe to, for people that want the old way.
> 3) If I reply to an email, then it gets posted as a reply to the
> topic in the forum.
Either or both of those are possible, given programming. They would definitely require non-trivial custom programming in PHP, with probably C or Perl scripts to glue together with sendmail. I don't know how it would work, but it would need to be designed, tested, etc.
Forum software isn't typically written to work that way. The board interaction is what they are about, and the e-mail notification features are a convenience to cue people that they need to go visit the forum because something has come up in their area of interest.
I think that's the wrong way to go anyway for other reasons.
E-mailing into a forum, i.e., by mail to firstname.lastname@example.org
or whatever getting auto-posted into the forum would set us up for spam to get injected into the forum. We could program around that, e.g., by having a secret archival address that is subscribed to the forum mail list or something. We do that to get our mail lists posted to the hypermail archives. Again, it would need to be designed, etc. The backend of the forum is an SQL database into which these e-mail messages would need to be injected. This raises lots of questions about format, quoting, character sets, attachments, etc, in the stuff that gets injected into the SQL database. I don't think we want to do that much customization. It would lead inevitably to a significant maintenance burden.