Marking 20k emails as read

from blog lmno.lol @alvaro, | ↗ original
Mbsync and mu4e are great for syncing and handling IMAP email. I've now migrated 4 email addresses, including an old Yahoo account. I wanted to mark all my Yahoo unread emails as read. Yahoo's webmail enables marking 500 emails at a time, making the process a little tedious. Mu-discuss has a handy thread, highlighting that moving/renaming synced...