I had issues with blacklisted server IP so the forwarding failed and e-mails were lost (could not find anything in "/var/spool/".

Here is the relevant "/var/log/syslog" log about the failure (adresses/IP/FQDN were redacted):

Feb  6 10:11:08 mail-server postfix/smtp[1049]: 4P8L3r2LLdmYveJ: to=<user-bar@example2.com>, relay=spool. mail.example2.com[192.0.2.1]:25, delay=0.28, delays=0.05/0.01/0.14/0.08, dsn=5.7.1, status=bounced (host spool.mail.example2.com[192.0.2.1] said: 554 5.7.1 Service unavailable; Client host [192.0.2.3] blocked using pbl.spamhaus.org; https⁖//www·spamhaus·org /query/ip/192.0.2.3 (in reply to RCPT TO command))

IP problem is now fixed (I hope) but I would like to avoid loosing e-mails in the future.

Because, in such case I cannot forward them to a special fallback e-mail address with certitude the sending won't also fail I was thinking of writing them on the filesystem (or at least, because I think they are somewhere in the first place, not deleting them once final failure is detected).

It there a way to do such thing? Is there a better alternative solution to my problem?

Thanks

REQUIRED BASIC INFO:

• iRedMail version 1.5.1

• Deployed with: the iRedMail downloadable installer

• Linux/BSD distribution: Debian 10

• mail accounts storage: MySQL

• Web server: Nginx

• Manage mail accounts with iRedAdmin-Pro?: No