Is it OK to delete messages directly from the Maildir via a cronjob?

Hi,

I've Googled and not found anything definite on this, so I'll try here.

Is it OK to delete messages directly from the Maildir via a cron job
rather than using an email client? Whilst I know that each message is an
individual file in the Maildir, is there any kind of index file that
would be out of sync or corrupt if I did this?

We're using Postfix 2.1.5 and Courier-IMAP 3.0.7-3.2 on SuSE 9.2.

The reason for asking is we setup Learn_HAM and Learn_SPAM folders for
users to copy their incorrectly identified spam & ham and the we use a
cron job overnight to learn from these directories. The users are then
supposed to delete this learned stuff from these directories with their
mail clients. However, this last step gets forgotten. Whilst this
doesn't do any harm (spamassassin knows if it's learned a message
already) it's a waste to keep going over the old messages again and so
we want to have the cron job delete all the messages (using bash's rm)
from /cur when sa-learn has completed.

Can anyone see any problems with this?

A second question is the use of alt.comp.mail.postfix and
mailing.postfix.users down to personal preference or is there some
differentiation between them? Them both seem to include technical
questions and so it wasn't clear where I should post this.

Thanks, David