(interactive (company-begin-backend 'notmuch-company))
(prefix (and (derived-mode-p 'message-mode)
(looking-back (concat notmuch-address-completion-headers-regexp ".*")
(interactive (company-begin-backend 'notmuch-company))
(prefix (and (derived-mode-p 'message-mode)
(looking-back (concat notmuch-address-completion-headers-regexp ".*")