Very recently on several groups.io lists I moderate, I am seeing list members with aol.com e-mail addresses unsubscribed (groups.io e-mail flagged as spam by their e-mail provider), most immediately rejoin with the same AOL e-mail address.
About a month ago Oath blocked e-mail delivery to my aol e-mail account unless I took the OATH pledge to hold Oath blameless no matter what. I took the Oath pledge and my e-mail delivery resumed.
For those unfamiliar with Oath; it is a new company created after Verizon acquired Yahoo and AOL. It's business plan is as a mobile media provider and to date it has been unclear about plans of YahooGroups and the e-mail providers it acquired. What has been clear recently is that Oath has gone from dormant to aggressive. They certainly have the ability to identify Oath customers who have left Oath for lists on Google, Facebook, and groups.io Of those three list host competitors, groups.io is definitely the weakest and most vulnerable. And if your e-mail provider is now part of Oath or controlled by Oath and you haven't taken the Oath pledge; Oath's current action may seem like harassment.
I fully understand those who won't take the Oath pledge, when as a list owner on YahooGroups, I refused; However delivery of my AOL e-mail was a different story and I surrendered. If you do not want to take the Oath pledge, I recommend getting a non-Oath e-mail account and using that for your list membership on groups.io
HO and Sn42