I have implemented the "change password" on Roundcube for HMailServer.
HmailServer is a free, open source MTA for windows with POP3, IMAP,SMTP interfaces.
To change password in HMailServer needs to use COM+ library
I implemented change password with a COM() function of PHP and enabled "IUSR_Machine" user to launch it.
I don't have time to make a pacth o a plugin
If anybody want to help me, i am happy to share my work.
I think to implement also an "autoresponder" soon.
I hope I'm not alone that use windows server in an open source project
Bye