Filtering spam e-mail based on sender's top-level domain

[goldberg]

During May the number of spam e-mails to my IDNet inboxes has been steadily increasing.
Several hundred per day now.

Applying filtering rules is a bit like aiming at a moving target - the IP addresses and mail addresses of the senders keep changing.

One type of filtering rule that would help is the ability to block whole top-level domains.
I already apply a From: filtering rule for domains such as .xyz which constantly sends large amounts of spam.  This rule works well because few if any of my valid e-mails contain this string.

Among many other problem domains, the one I would really like to block is .co but applying a From: filtering rule for the string .co would also block .co.uk and .com among others.

Have any other IDNetters found a way of blocking mail from whole top-level domains ?

Is this not something IDNet could usefully do on our behalf ?
It's very unlikely I would ever want to receive e-mails from domains such as .xyz and .co

[Simon]

I wonder if putting .co in quotes (so, ".co") would work by blocking that specific 'word'?  Might be worth a try, or you could check with IDNet first.