For the last 25 years I've used Rocketmail (now part of Yahoo) via webmail and Windows 10 Mail without a problem.
Today, I've installed Microsoft 365 as a member of a family group.
While looking at Excel (NOT Outlook) a window appeared and KIS 188.8.131.520(b) Web Anti-Virus reports:-
Event : SSL connection with invalid certificate detected
User type : Not defined
Application name : EXCEL.EXE
Application path : C:\Program Files\Microsoft Office\root\Office16
Component : Web Anti-Virus
Result description : Blocked
Object name : autodiscover.rocketmail.com
Reason : Invalid name of certificate. Either the name is not on the allowed list, or was explicitly excluded.
Best answer by Wesly.Zhang
I think autodiscover.rocketmail.com is on repairing their website now……