No expert, but if it is a temporarily allocated IP address that as been blacklisted, hasn't someone got something wrong at the blackilst supplier end ?
Sorry, I meant whether it's the individual IP address or the entire range. Isn't it the case that entire class C addresses have found themselves on DNSBLs...?
It rare for a range to get blocked, and if an ISPs entire range (or a fair chunk of it) had been blacklisted I doubt it would be for too long, the ISP would soon be onto that one.
The other option is, of course, that BMs machine has been compromised by a botnet and has been sending out spam which caused her IP to be blocked. as a precaution you may want to run a full scan with malwarebytes.
Right I'll do that first. Although had i been sending out loads of spam I have no doubt SOMEONE would have told me.
Whilst I have been messing about this this one of the cats has nicked one of the chicken breasts I put out to roast off for tea. It just gets better and better.
the sort of botnet that would get you blacklisted wouldn't just be sending mails to your contacts, it would be sending 10s of thousands of mails to different people.
We got a computer infected where I work resulting in our IP getting blacklisted a couple of years ago, that didn't go down too well :)
As Chuck says, most owners of "zombies" don't realise that their machine has been compromised. They often notice the degradation in performance, but usually put that down to other things.
Generally you should be using your ISP's SMTP server for out going mails, or, if not the email address providers along with authentication. and as such your own IP address shouldn't matter.
Your error seems to suggest you are running a local SMTP server and that's not normal.