I have no idea how a variety of clergy and diocesan addresses, plus most of the churchwardens north of Ipswich all got marked as "spammers" by Hotmail. Nor do I much care, since the affected folk no longer use Hotmail.
I got the impression from your post that your system was a WAN with a central server that handled e-mails, if it is then it would only be that server that would be on the black list, not the individuals. It should be mentioned to your IT guru just incase there is an issue, after all, hotmail must have some reason to have decided your e-mails were junk
I was trying (and failing, it seems) to warn people to search out and check that little word "Junk" on the mail page of their Hotmail.
that's a bit grandma/eggs on this forum
but I know what you mean.
The real problem lies with the people who said use hotmail and perhaps even set it up for them but didn't bother to explain these things properly. If I'm asked then I sit and guide them through the set up procedure (it's better if they do it, it gives them confidence....well usually) I then go through the thing with them getting them to click on all the basic features and explaining what it does and most certainly and explanation of junk mail would be included.