I guess the real issue here is to figure out two things:

1) how to have a "cron" (scheduled tasks) infrastructure within mantis. One can rely on external cron jobs or have an internal task manager. There are a few solutions for this:

• external cron jobs: http://www.webcron.org/, http://www.cron-server.de/
• internal cron: http://drupal.org/project/poormanscron

2) have a way to list all those bugs, with the email contacts and make up a mail to actually send, recording all this in each bug's history.

3) anything else?

At any rate, the general approach should be to build a script that does the actual necessary work and let it be called as http://bugs.mantis.org/cron.php.

A.

Some scripts that I've used, which can do fake and/or real cronning (cronning?) require for you to (un)check a box to toggle the fake cron.
I like that, but I would like it more if it could try to add the cron entry automatically first. I see the process a little like this:

• ask how often the cron job should execute
• generate the cron command-line thing
• try to execute it (backtick operator? check that we're actually on unix first?)
  then either
  1: cron attempt successful, congratulate user, fetch beer
  OR
  2: cron job fails, send user to error page which:
  2a: Shows the command-line string "just in case" they can do it by hand after all
  2b: the error message from the system, if any
  2c: the error message from php, if any
  2d: remembers the post data - if they're on windows it might be a handy creature comfort to be able to copy what they already decided straight from their browser to task-scheduler or whatever windows has.
  2e: offers the option to do a "fake cron" with that data
  2f: (maybe) offers to use some kind of weird hosted web cron thing

using a web based cron thing instead of one installed on the system?? That idea seems freaky. Would that be slow? Does it send in an email when the job iterates? Scary thought.

NB for 2f, on that page all you might be doing is taking options for setting something in the database. Your webservices script or whatever may only have to receive data and flip a switch.
2e could be even easier because it might only mean sticking something in the database
And of course ideally you just want "1:"

I might provide the code from my RSS posting plugin (not my work, but I have a copy) if it is GPL and I remember to do it.