Member Email Bouncing

Club number 6348

All emails to one of our members keep bouncing while they get delivered if I send the email directly. Does anybody have an idea of how to resolve this?

The error message I am getting is below

ron@fitnessking.com appears to be an invalid or non-working recipient email address. (No advertised SMTP servers are accepting mail.)

*** Please check the email address to make sure it is not misspelled. ***

If you believe this warning is incorrect, please visit support.toastmastersclubs.org and post a support request message

Regards
Amit

Without your club number there is nothing we can do to assist you.

My bad. The club number is 6348.

That email address has not worked in over 4 weeks.
Ron hosts at a data center that houses spammers who frequently spam FTH and the IP was blocked.
I have removed the block for now, but it could happen again.