According to
Wikipedia iCloud, Protonmail and Tutanota never expire. Weither that is correct or not is a different question alltogether, it's Wikipedia after all.
Also a lot of providers are not listed in that comparison (eg EUMX, ContactOffice, Safe Mail, Posteo, Walla, Virgilio, Seznam, ...) while strangely enough some of those do have Wikipedia pages but they're not connected to the comparison of webmail providers. Posteo for example has a Wikipedia entry in
English and in
German, ContactOffice has a page in
Dutch .
Seznam has a page in English, Virgilio.it
too , ...
In other words, better not just assume those services who according to Wikipedia have no inactivity limit, indeed never expire ... if any of those services appeal to you, doublecheck if that info is correct.