We are also seeing more messages classified as spam with OJS 3.1.x compared to OJS 2.x.
At first I suspected that in part the fact that OJS 3 sends several notifications without content, but indicating a link for the content to be seen when accessing OJS caused some users to mark the message as spam and training their supplier (gmail, outlook ) to do this automatically in the next similar messages.
Elsewhere, that the fact that they are short messages (without the content) with almost only one link, would be detected as suspected spam more easily by some providers.
But currently the biggest problem we are seeing is quite different: there are many “fake” registrations occurring that manage to circumvent google recaptcha in some way.
These “fakes” users use many non-existent addresses. When OJS tries to send messages to them, it reduces the IP reputation of the server. If these users are not excluded, the problem is aggravated with each new sending attempt.
In this sense, we will try two actions:
- Encourage e-mail confirmation requirements in the registration, see Spam users registration despite of recaptcha - #2 by israel.cefrin
or How do I combat SPAM? - Use additional plugins: Removing spam registrants - #4 by ctgraham