There are countless ways to build an autoresponder. I normally think of sendmail as an MTA (mail tranfer agent) and not an MDA (mail delivery agent) or MUA (mail user agent). The autoresponder function is often in the MUA (when controlled by the users) or the MDA (when responding more generally).

There is no technical reason that sendmail rules and config files cannot be used as a software platform for user autoresponders. There are just easy places to do user level filtering and autoresponding.

I use sendmail for domain and IP address antispam and relay filtering for entire organizations using the sendmail macros, running sendmail as an MTA. For autorespondering, I use my MUA (which is Outlook). So, I use a combination of UNIX-based sendmail, POP and IMAP for the 'backoffice'. If I'm on the servers, I can read and manage mail with elm and other UNIX-ish MUAs. However, most of my email management is done from the Windows desktop now.

I have found, over the years, that it is best to use software like tools in the tool chest. I don't hammer nails nor turn bolts with pliers. I don't user screwdrivers to take nails out of a board. What does this mean.

I use UNIX in the back office. I use Microsoft (Win98 to be exact) to read/manage mail, run my browsers, do slide presentations, write big documents. I receive mail and filter on UNIX. Proxy on UNIX. Firewall on UNIX. Run DNS on UNIX. Run Web services on UNIX. Run SQL databases on UNIX. My MS laptop clients talk seamlessly to the UNIX-based infrastructure.

As far as mail filtering goes, that can be done on the UNIX MTAs and on the MS laptops running Outlook (I use both). Which UNIX? I run Linux, have for over 8 years. and will be running Linux 10 years from now (it would seem). I do not write documents in VI/LaTeX and read my mail with ELM quite as much as I used to

I also have web-based interfaces to most of my subsystems, including mail, SQL admin, system admin, etc. So, when I'm not on my wireless laptops at home, perhaps in a coffee shop or kiosk, I have web-access to the subsystems.

The is getting off topic, but the bottom line is that both 'thick clients' and 'thin clients' have their place in this world. Pure 'broswer based Internet appliances' without a robust OS, many utilities and disk space are not my 'cup-o'tea'; but I can see how they would be useful in phonebooths, in the car, on the boat, in the air, in the grocery store, at the ATM machine, etc. where personal storage and personal processing is not a driving requirement.

Sorry to be drifing off topic....