>Full-text search is entirely client side (not via IMAP)

Setting up server-side Xapian full-text search and disabling the crap client-side one in Thunderbird was one of the best improvements I made to my email usability. What makes your client-side search better? It's usually not speed I'm looking for, but rather precision, such as double quoted phrases (sorely missing from Thunderbird's client-side search), filtering by a mixture of things, etc.

I wish more clients had an option for server-side-only search (looking at you, iOS Mail.app) and/or had a nice UI for it (ctrl+shift+f dialog in Thunderbird is janky but gets results)