[horde] How to migrate a user from one mail address to another?

[Michael Brohl]

Hi everyone,

one of our users needs to have his email address changed due to a name 
change.

Is there a proposed way to migrate his mail, calendars, notes, sieve 
filters etc. from one email to another on the same server?

We are using Horde webmail 5.2.22 with postfix, dovecot and mysql with 
virtual users.

Any hint is appreciated, thank you!

Best regards,

Michael