"imap", "pop3", "webmail", or "system".
So out of curiosity, which one of these do I use? Is it the service I'm connecting from? Or the service of the password I'm changing? (which doesn't make sense since the password is global).
The service of the password being changed. Note that not all authentication modules will make use of this field.
pgp00000.pgp
Description: PGP signature
