I use a four-pronged attack on high probability domains via custom filters (edit: Antispam 'custom rules');

I am missing something Steve. I see where I can do some filtering at the domain level. I know I can do at the user level. I have no problem creating the first and then exporting and doing for all users. I just don't see where to do this as there is no import/export option for wherever I am looking. I don't see an area on the spam settings (server wide) that would allow this either.

Although I know I want to block all of these at times I could see not wanting that and it would be a domain level type of setting.

Sorry, I've said 'custom filters' rather than Antispam 'custom rules', which may have confused you?

Hi Rod. I'm having the same issue with enormous amounts daily of spam from .icu, .best and .monster. SMTP Blocks are requiring a full domain or email address (when entering *.icu = This is not a valid domain or email address.)  therefore this solution cannot be enabled. Any other suggestions? I appreciate your help!!

We have the same problem, with mainly .icu .top and .best domains.

There needs to be a much easier way to block these

There is a link on an older thread that talks about adding on additional definitions for Clam. I found this company has some pretty good definitions and I see a lot of those same TLDs in my list. They charge something but it is not a lot per year. https://www.securiteinfo.com I do not use all the signatures they have, I found some are a little aggressive. My server updates signatures two times a day.

If you need help with the set up I can see if I have my old instructions and all the old set up files.

same issue here...

Hi to those still having issues, I gave a solution that adds weight to a weight based approach. There is more overhead in this solution but is good for service providers that cannot just 'hard block' domains..

'Employee Replied' gave a simple 'hard block' for domains, I've tested this functionality in 7242 without any issues.
"At the system level, you can go to Settings >> Security >> SMTP Blocks.  Add a domain block for *.icu"  

Are any of you having issues with the simple approach, if so, what version are you running?

Just added a few TLDs and saw a few already blocked. Thanks, they really had this useful feature buried, when I saw the post originally I did not see it, but I was on an older version.

My list so far is: *.icu, *.best, *.top, and *.xyz I know it will grow.

Now after a reboot it's functional even for me...