I went into my Sent messages folder (em client) to look for an old message and discovered one that was sent on July 31, 2017, apparently from me, to this address: leave-fd8215781a3c402029-fe511d777061027e7d17-fef61175736702-fe9613737564027970-ffc71c@leave.emails.avast.com
No subject, no message, just from (me) and to (address above). Anyone know what this is?
