Background
Greylisting is a common technique to keep once-off spammers away from a mail server. By using timing and a triplet system based on sender IP, sender email, and recipient email, it puts a hold on the message relying on legitimate email servers ability to retry after receiving a 419. Clients don’t always love it because many people have become used to instant email, however, since this is typically only the first message, they don’t always notice. Where it falls flat though is with load balancer that have been poorly trained to do 419s.
Virtualmin has an interface to control the hosts, which is much more advanced than cPanel because with cPanel you can only add the IP address.
To use it, is pretty simple.
Login as root.
Navigate to this section below left where the admin functions are:
Email Settings -> Email Greylisting
Add new SMTP to Whitelist
Mail server IP address or hostname: fedex.com
Additional comments
Always add a comment.
Use a regex if needed.
Customizations
I’ve noticed with newer Virtualmin installation the list has grown a lot. Unfortunately it seems that Virtualmin doesn’t update this list, even if you are a pro user. For our environment we have added these customizations:
- directmail2.binance.com
- sendcloud.org
- fedex.com (be careful though because this is a popular scamming domain)
- medirates.co.za
- name-services.com
- wordfence.com
- synaq.com (24 September 2024)