Blocking Invalid Outgoing Senders

[infinityM]

Hey Guys,

Ok so I am using Proxmox Mail Gateway... So far so good. Few hickups but overall it works well...

The only thing is I am worried what happens if the IP get's blacklisted by accident... So I have 2 questions...

1. Is it possible with PMG to assign a second IP, and should the first get blacklisted, I switch outbound email to route through that one instead?
2. Is it possible to have proxmox blacklist recipient addresses that are invalid? That way when someone tries to send over and over it would get blocked by our Proxmox not by the receiving server and then them reporting us for spamming...

It does not happen often, but I have received a few complaints over the years... So I would love to mitigate that a bit.
I would think that if a mail bounced for reasons like the domain does not exist, or user does not exist blacklisting the recipient for x hours or days might be beneficial to prevent spamming a little bit more...

PS. What does PMG do to prevent outbound spamming?

 

[hata_ph]

1. Set up another smtp server, configure it as your PMG's smarthost or add in transport to relay your outgoing mail.
2. If your email users in LDAP, PMG support LDAP query. Create a who object filter to block invalid users.

 

[Stoiko Ivanov]

1. Is it possible with PMG to assign a second IP, and should the first get blacklisted, I switch outbound email to route through that one instead?

not via GUI - you can configure a second IP, and modify the entry in /etc/hosts for your pmg-hostname to the other IP and run `pmgconfig sync` and reboot afterwards, or you adapt the configuration of postfix and switch over in the master.cf - see https://pmg.proxmox.com/pmg-docs/pmg-admin-guide.html#pmgconfig_template_engine

2. Is it possible to have proxmox blacklist recipient addresses that are invalid? That way when someone tries to send over and over it would get blocked by our Proxmox not by the receiving server and then them reporting us for spamming...

You mean recipient verification (currently this works for inbound mail (to you) - but again, by adapting the master.cf template you could add it to outbound mails as well)
https://pmg.proxmox.com/pmg-docs/pmg-admin-guide.html#_mail_proxy_configuration

I would think that if a mail bounced for reasons like the domain does not exist, or user does not exist blacklisting the recipient for x hours or days might be beneficial to prevent spamming a little bit more...

for outbound mails - PMG generates a bounce and notifies the sender - otherwise your users would not know that they mistyped an address and that their important mail never reached the recipient?

PS. What does PMG do to prevent outbound spamming?

You can configure PMG to scan outgoing mail for spam in the Mail Filter/Rule System (the rule is in the default ruleset, but not activated by default -> Block outgoing spam)

I hope this helps!