I'm getting this a lot from situations such as people that have deleted me by accident then re-added me, not known who I was, blocked me, then added me, or people who have had to block multiple other contacts (including myself) and unblock.  Everyone except one person swears that I'm added in their list except one.  Unfortunately, none of them run messenger plus to see if it shows them as being in my list.

What makes me wonder that this may be a fault is this: someone whose contact information will say "you are not in this contact's list" will message me a good 12-16 hours after our last chat, sometimes on a different client than they were using.  Now the thing is - they started the chat.  How could they open a conversation with me, if I wasn't in their list?

It boggles the mind, and short of asking them to show me a screencap of their contact list (which understandably is a bit of an unusual request, especially if peoples' full emails are in it), I have no idea what's going on...

Please read Contact List Clean-Up NOT Working - Information!