;; This sets `mu4e-user-mail-address-list' to the concatenation of all
;; `user-mail-address' values for all contexts. If you have other mail
;; addresses as well, you'll need to add those manually.
(setq mu4e-user-mail-address-list
(delq nil
(mapcar (lambda (context)
(when (mu4e-context-vars context)
(cdr (assq 'user-mail-address (mu4e-context-vars context)))))
mu4e-contexts))))