For the last two months, a lot of my emails to a person I've emailed a lot, and who does not have Shaw, suddenly stopped going through. They have supposedly been returned because of spam but these emails do NOT contain spam in any way. A search of IP addresses in the return message comes up clear when checking blacklisted IP addresses, except for one that indicates Shaw which shows blacklisting on some sites. The message I get back when the email doesn't go through, indicates "Client host [Shaw IP number]...blocked." That IP is the same Shaw IP.
The message I get back also says: Threat Look Up URL referring to the an IP checking website which this message won't let me include in the message. When I look up that Shaw IP in that website, it shows a threat level due to "Spam sources".
Does this mean that this Shaw IP is known for marking spam and therefore is blacklisted? Why would my emails be blocked in this way when they are clearly not spam. Some times I can have 4-6 emails return...and then suddenly one goes, then more don't go. There's no reason why these emails should be blocked.