Find Max() updated time for a group of users

Database is MariaDB 10.3.25 I have 2 columns that are relevant: UserID and LastUpdate UserID consists of user@domain LastUpdate is a date field. Here is my issue - I have the current query: select a.UserID, substring_index(a.UserID, '@', -1), max(a.lastupdate) from MyTable a group by a.UserID having max(a.lastupdate) < '2020-03-31' This shows all the Users that haven't updated in just over a year and the domain. However there is the following scenario that I want to account for: UserID LastUpdate A@A.com 2020-08-16 B@A.com 2019-05-16 C@A.com 2021-05-05 With the current query, B@A.com will be captured, and therefore domain A.com will be captured as not in use, but the user C@A.com is still active - I want to do a Max(a.lastupdate) but have it grouped by substring_index(a.UserID, '@', -1) but also spit out all the users for that domain. I'm sure the answer is starring me in the face...