Unable to add XXX because host YYY is listed on RBL dnsbl.sorbs.net
What does this mean? I get it sometimes, but not regularly.
Unable to add XXX because host YYY is listed on RBL dnsbl.sorbs.net
dnsbl.sorbs.net is a database of spammer's DNS names. Basically anything on that list spammed someone at one time or another so these people add it to that list and it replicates around and is blocked
It's a real time black list. The reason you probably only get it when you e-mail your mom is because the company she works for uses that exact RBL to block spam. Most RBLs will not block known spammers, but rather only block e-mail servers that are found to be open relays. Basically, if they see that your primary e-mail server is vulnerable to being abused for spam purposes, then they just block it.
You can normally get it removed, but they are all strict about it and say not to request removal until the problem is fixed. All while not providing you why you were blocked in the first place.
Some RBLs are better than others. Some blanket add IP addresses or domain names and have horrible tracking systems. If your mom is the IT person where she works, then she may have put it there to block you, but it's not likely.
It bothers me that not only do I not understand most of the posts in this forum but now I don't even have a clue about the name of this thread.