Steps to reproduce:

1. Add additional identity second-mail@example.com in mail settings > imap
2. Set third-mail@example.com as Reply-To address to the additional identity second-mail@example.com
3. Send an email using the second identity (second-mail@example.com) to an external recipient

Note: the account is allowed to sent e-mails from any address configured as additonal identity or set as Reply-To address.

Expected result: If the external recipient answers the mail sent, the mail should be sent to third-mail@example.com (Reply-To address configured before)

Actual result: The answer e-mail oft he external recipient is sent to second-mail@example.com instead oft he configured Reply-To address