Version:           1.7.2 (using KDE 3.3.2 Level "a" , unofficial build of SUSE )
Compiler:          gcc version 3.3.3 (SuSE Linux)
OS:                Linux (i686) release 2.6.5-7.111.30-default

Users sometimes switch mailadresses for various reasons.
Often the old adress is polled for some time after the
decision to switch is made and some months later the old 
account is being removed.

KMail already uses the users' sender identity
which an incoming mail was sent to as the sending
identity in replies. How about marking an identity
as obsolete in the account setup and specify an
different identity (via drop-down box) for replacement?

Behavior could be:
When automatically determining the users' identity
for replys do it as before. If that identity is marked
as obsolete and to replace by a different one then
use that one.

This way people would have an comfortable and
easy-to-use way of distributing their new mail address.