I have having issue also ( Mautic 2.2.1), an HTTP 500 when sending a “custom email”
[19/Nov/2016:00:08:39 +0100] "POST /mautic/s/contacts/email/3215?mauticUserLastActive=1&mauticLastNotificationId= HTTP/1.1" 500 55137 "http://srv04.mydomain.com/mautic/s/contacts" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.59 Safari/537.36 OPR/41.0.2353.46"