A new configuration setting has been added that, if enabled, allows users to set a seprate 'reply-to' address for each mail account. The new setting can be found in the ui.properties:

ui/mail/replyTo/configurable = false

The feature is disabled by default.

If enabled a new field 'Reply-to' will be available in the mail account setup. This mail address will be added to each outgoing mail as reply-to address. If not set the default will be used. Additionally this field will be shown when composing a message and a user will be able to change it before sending the message.