Note, mu4e supports built-in address autocompletion; Address autocompletion, and that is the recommended way to do this. However, it is also
possible to manage your addresses with org-mode, using
org-contacts.
mu4e-actions defines a useful action (Actions) for adding a
contact based on the From:-address in the message at point. To
enable this, add to your configuration something like:
(setq mu4e-org-contacts-file <full-path-to-your-org-contacts-file>)
(add-to-list 'mu4e-headers-actions
'("org-contact-add" . mu4e-action-add-org-contact) t)
(add-to-list 'mu4e-view-actions
'("org-contact-add" . mu4e-action-add-org-contact) t)
After this, you should be able to add contacts using a o in the
headers view and the message view, using the org-capture mechanism.
Note, the shortcut character o is due to the first character of
org-contact-add.