There's an issue with sending mail through Syncroton, when SSL is disabled;
- For some reason, the DOM seems to be NULL, which isn't getting handled correctly (see T1052#15103). This matter probably deserves some investigation, and could be split out in a separate ticket if so needed,
- Syncroton should probably not be attempting to connect to the SMTP / submission server for an email submission attempt it can reasonably know is going to fail,
- A better error message could be used.