Messages sent by the bot are stored as writeTemp

[XayOn]

Apparently, upon sending mails, everything outputted by the client will be sent too, as it has been received as events and stored on the database as message body / subject. I've no experience on GO/gomatrix, but I think you should check evt.Sender to discard messages sent by the bot itself.

Matrix-EmailBridge/main/Main.go

Line 279 in cafb530

if evt.Content.AsMessage().MsgType == event.MsgText {