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Basic Pleskian
- Server operating system version
- CentOS Linux 7.9.2009
- Plesk version and microupdate number
- Plesk Obsidian 18.0.44 Update #2
We're having issues with our IP reputation on one of our servers causing some remote mail servers to now reject, or spam, emails sent from any domain that this server hosts and I think I've discovered the cause.
Looking in the mail logs, it seems we're receiving a lot of mail sent to random fake addresses, all ending in the servers hostname, and these are of course being rejected with "Recipient address rejected: User unknown in virtual alias table" responses. These always have Russian helo address too, e.g. "helo=<mr0.ulstu.ru>" so I think what's happening is that malicious mailers are sending to fake addresses at known server hostnames, to trigger bounce back emails to honey-trap addresses or at least increase the volume of mail to obscene amounts. According to senderscore.org our outgoing mail volume for this IP address has shot up to around 380,000 per day!
So, is there any way to disable the bounce back emails when mail is received to fake addresses? Or a better solution? Either within Plesk or the Postfix config?
Looking in the mail logs, it seems we're receiving a lot of mail sent to random fake addresses, all ending in the servers hostname, and these are of course being rejected with "Recipient address rejected: User unknown in virtual alias table" responses. These always have Russian helo address too, e.g. "helo=<mr0.ulstu.ru>" so I think what's happening is that malicious mailers are sending to fake addresses at known server hostnames, to trigger bounce back emails to honey-trap addresses or at least increase the volume of mail to obscene amounts. According to senderscore.org our outgoing mail volume for this IP address has shot up to around 380,000 per day!
So, is there any way to disable the bounce back emails when mail is received to fake addresses? Or a better solution? Either within Plesk or the Postfix config?
