I check the news and finance. Quite a few relatives use Yahoo! mail and fortunately its UI has been relatively static for the past half-decade [0] (although AOL mail takes the cake in the static -- and usable -- UI department [1])

[0] https://en.wikipedia.org/wiki/Yahoo!_Mail#2011%E2%80%93prese...

[1] https://thenextweb.com/news/aol-mail-gets-a-refresh-would-li...