mu4e: Add SMTP config

lisp/init-mu4e.el.template

                                                                ".*@home.example.com")))
            :vars '( ( user-mail-address	    . "aliced@home.example.com"  )
                     ( user-full-name	    . "ßingen" )
-                    ( mu4e-compose-signature . nil)))
+                    ( mu4e-compose-signature . nil)
+                    ( mu4e-sent-folder . "/Sent")
+                    ( user-mail-address . "aliced@home.example.com")
+                    ( smtpmail-smtp-user . "aliced@home.example.com")
+                    ( smtpmail-local-domain . "example.com")
+                    ( smtpmail-default-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-service . 587)
+                    ( smtpmail-stream-type . starttls)
+                    ( smtpmail-use-gnutls . t)))
          ,(make-mu4e-context
            :name "Work"
            :enter-func (lambda () (mu4e-message "Switch to the Work context"))
                            (string-match-p "^/Arkham" (mu4e-message-field msg :maildir))))
            :vars '( ( user-mail-address	     . "aderleth@miskatonic.example.com" )
                     ( user-full-name	    . "ßingen" )
-                    ( mu4e-compose-signature . nil)))
+                    ( mu4e-compose-signature . nil)                    (mu4e-sent-folder . "/Sent")
+                    ( user-mail-address . "aliced@home.example.com")
+                    ( smtpmail-smtp-user . "aliced@home.example.com")
+                    ( smtpmail-local-domain . "example.com")
+                    ( smtpmail-default-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-service . 587)
+                    ( smtpmail-stream-type . starttls)
+                    ( smtpmail-use-gnutls . t)))
 
          ,(make-mu4e-context
            :name "Cycling"
                            (string= (mu4e-message-field msg :maildir) "/cycling")))
            :vars '( ( user-mail-address	     . "aderleth@example.com" )
                     ( user-full-name	    . "ßingen" )
-                    ( mu4e-compose-signature  . nil)))))
+                    ( mu4e-compose-signature  . nil)
+                    ( mu4e-sent-folder . "/Sent")
+                    ( user-mail-address . "aliced@home.example.com")
+                    ( smtpmail-smtp-user . "aliced@home.example.com")
+                    ( smtpmail-local-domain . "example.com")
+                    ( smtpmail-default-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-server . "smtp.example.com")
+                    ( smtpmail-smtp-service . 587)
+                    ( smtpmail-stream-type . starttls)
+                    ( smtpmail-use-gnutls . t)))))
 
 ;; set `mu4e-context-policy` and `mu4e-compose-policy` to tweak when mu4e should
 ;; guess or ask the correct context, e.g.