[feature suggestion] Mail messages configurable

### ‎ Can you make the mail messages configurable? Some ideas: - use other address than `root@localhost.localdomain` - use notifications instead of cron messages, or both - completely en/disable - option to turn off mails that repeat previous information Currently the postfix mail is flooded with messages like this: ``` From root@localhost.localdomain Fri Apr 10 17:15:00 2026 Return-Path: <root@localhost.localdomain> X-Original-To: root Delivered-To: root@localhost.localdomain Received: by localhost.localdomain (Postfix, from userid 0) id D6404241EFD; Fri, 10 Apr 2026 17:15:00 +0200 (CEST) From: "(Cron Daemon)" <root@localhost.localdomain> To: root@localhost.localdomain Subject: Cron <root@localhost> /usr/bin/nice -n19 /usr/bin/ionice -c2 -n7 /usr/bin/backintime --profile-id 7 backup-job >/dev/null MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Auto-Submitted: auto-generated Precedence: bulk X-Cron-Env: <XDG_DATA_HOME=/root/.local/share> X-Cron-Env: <XDG_CACHE_HOME=/root/.cache> X-Cron-Env: <XDG_CONFIG_HOME=/root/.config> X-Cron-Env: <XDG_STATE_HOME=/root/.local/state> X-Cron-Env: <LANG=en_US.UTF-8> X-Cron-Env: <SHELL=/bin/sh> X-Cron-Env: <HOME=/root> X-Cron-Env: <PATH=/usr/bin:/bin:/usr/sbin:/sbin> X-Cron-Env: <LOGNAME=root> X-Cron-Env: <USER=root> Message-Id: <20260410151500.D6404241EFD@localhost.localdomain> Date: Fri, 10 Apr 2026 17:15:00 +0200 (CEST) Status: O ERROR: Unable to extract licenses from LICENSES directory "None". WARNING: The flag "--profile-id" is deprecated and will be removed from Back In Time in the foreseeable future. Use "--profile" instead. Feel free to contact the project team if you have any questions or suggestions. WARNING: The command "backup-job" is deprecated and will be removed from Back In Time in the foreseeable future. Use "backup --background" instead. Feel free to contact the project team if you have any questions or suggestions. ```