Every day there is at least one attempt from a dynamic IP address at hinet.net to relay email through my mail server.
Is it worth my while blocking this completely ?
And if it is, how do I go about it ?
Note: all our domain mail is delivered via an offsite mail sanitiser - so 99% of it comes from a single IP address. The other legitimate server connecting are our own off site servers. So if it easier to specifically allow just a few networks - rather than to specifically block just a few networks - I would be happy to do it that way too.
Thanks in advance.