I forgot to say that I have a “Yes” on the “Process emails in background?” option in the QSM plugin main settings. With a “No” the emails come back all with that error.
Another interesting clue I forgot to mention: I left blank these 2 options in the QSM main settings:
– From Name (The name emails come from)
– From Email (The email address that emails come from)
If I write in these 2 fields the very same email and name that I force in the “WP Mail SMTP” plugin… I get the “Mailer: Other SMTP SMTP Error: data not accepted” error at every SMTP attempt.
