Checking for a secret key with format `<foo@bar.com>` may not work for
people that store key IDs in .gpg-id. Removing the `<` and `>` makes it
work for both beople that use emails and people that use IDs.

If -a is passed along with "$@", mailsync will sync all mailboxes even
if only a single channel is passed in with "$@". This breaks the
semantics of the `o` macro in mutt which should only sync the current
mailbox that is currently being viewed in mutt.