Just FYI --- the option in Squirrel to have "Server Side Sort" refers to the apps ability to use the imap server's "SORT" capability (if it exists). Otherwise, the webmail app needs to download all headers, sort them, then display recent ones (which can be very slow). Using "server side sort", you simply ask the imap server to sort the folder and give you most recent headers. MUCH faster.
Some clients give you the option of displaying (sorting) by received date or by sent date. But not all.... many just use the internal date header (which spammers take advantage of).