Reject Unknown Senders (reject_unknown_sender_domain) - Whitelist

[AechoOne1]

Good day,

we use PMG as a mail security gateway for our email systems. To improve spam filtering, we have enabled “Reject Unknown Senders.” The problem is that we receive various messages from our servers (e.g., Proxmox Backup Notification) that are sent from addresses such as servername.domain.com. Naturally, these are now being blocked because the domain is unknown. How can we whitelist these? We have a mail filter rule with the highest priority that allows our domains as well as all our IP networks. Additionally, our domain is listed as a regex under Mail Proxy => Welcome List. Unfortunately, the Postfix policy seems to take precedence over both of these. How can we resolve this?

Best regards

 

[Stoiko Ivanov]

please share the logs of such a mail being rejected.

 

[AechoOne1]

Good day,

nevermind. Domain Whitelist seems to work - my testserver sent with 2 different Domains, one whitelisted, anotherone not.

mx1 postfix/smtpd[2085161]: NOQUEUE: reject: RCPT from unknown[x.x.x.x]: 450 4.1.8 <root@servername.local>: Sender address rejected: Domain not found; from=<root@servername.local> to=<our@maildomain.com> proto=ESMTP helo=<servername.domain.com>

But one Question stays:

Can we configure the system so that IP addresses whitelisted in the MailFilter Rules can always send emails, regardless of the domain? We cannot put all our IPs in Mail Proxy => Whitelist, because the Mail Filter Rule has an Recipient.