Accidentally deleted Postfix

Hi, what is the best route to get postfix working again when it's accidentally deleted by installing an incompatible program please. I'm running ISPConfig Version: 3.3.1p1 on Debian GNU/Linux 12 (bookworm). Current positition is i'm getting no inbound or outbound mail.
Secondly, i've downloaded Email backups of the Postfix queue and Emails between the date of the last VPS backup image and the time of running a restore - what is the best way of reimporting the Emails please? Simply reverting the VPS backup doesn't seem to have resolved the issue.
I may have broke even more by trying to get AI to help me fix it. It started getting me messing with permissions, moving override files and all sorts.
Thanks

 

Initial Problem: Installed ssmtp (on Gemini's advice), which removed Postfix. Reinstalling Postfix broke ISPConfig mail configuration.

Actions Taken:

1. Removed ssmtp.
2. Restored server from Contabo snapshot (pre-ssmtp state) + restored recent emails from backup (/var/vmail + queue).
3. Cleaned stale lock files (/var/lib/postfix/master.lock), killed stuck processes.
4. Removed bad systemd override (/etc/systemd/system/postfix.service.d/override.conf) that caused "bad unit file setting".
5. Fixed TLS certificate symlinks in /etc/postfix/ (smtpd.cert / smtpd.key).
6. Ran multiple ispconfig_update.sh --force to reconfigure services.
7. Cleaned up various broken symlinks and lock files.

Current State:

• Postfix is running (active (exited)).
• Dovecot is working.
• Mail is processing (logins, deliveries visible in /var/log/mail.log).
• Remaining cosmetic warnings: old .bak symlink files in /etc/postfix/.
  
  How do I ensure Postfix/Dovcot is now configured how ispconfig expects to avoid further problems/hidden problems please including with Let's Encrypt SSL Cert renewals? Mail is coming in and going out.
  
  Thanks.

 

Thanks ever so much Till - I hope that you are well!