[Dovecot] valid folder name

We have a quite large user base, with lots of bad folder names because the mail folders was earlier accessible outside of dovecot. Now we're running dsync conversions from maildir to mdbox for all users, but are struggelig a bit with dsync not liking invalid folder names.

Before we convert a user we try to determine if the folder names are valid, but we don't have a very good regexp for validating it. Maybe someone else knows a way to verify (and fix?) folder names that are invalid.

The rules I know is:

• name doesn't start with '.' or '~' (after the initial '.')
• name doesn't end with '.'
• the name doesn't contain '..'
• the name is valid mUTF7

So, any regexp gurus that can distill those rules down to something usable?

-jf

-- Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. -jwz