I am trying to set up my account's IMAP settings. This tutorial <https://support.mozilla.org/en-US/kb/imap-synchronization> shows that in account settings, when I expand my account, there is a list of options, which should include 'synchronization and storage' (between junk settings and return receipts). But I don't see 'sync and storage'. I do see server settings, copies and folders, comp. and addressing, junk settings, disk space, return receipts, and security. The options I'm trying to set are "Synchronise all messages locally regardless of age" and "Keep messages for this account on this computer." But I don't see any options like that in any of the menus I can access.