You can do it easily from cron
(if you are on *nix) and most probably it can be done on Windows too. Calubre includes several command line tools, but for you the most important is ebook-convert(.exe)
.
With that you can create a mobi ebook from the RSS recipe like:
ebook-convert WHATEVER.recipe WHATEVER.mobi
Mailing can then be done like:
calibre-smtp -a WHATEVER.mobi -u [email protected] -p PASSWORD -r smtp.PROVIDER.com --port 587 [email protected] [email protected] ''
And set up a cron/scheduler job to automail it to you.
I'd recommend to read the fine manual.
(Note: this wont add the created mobi to your library! But you can do it with the calibredb
command as documented here)