The registration emails and review requests are not being sent to Gmail, Hotmail, Yahoo accounts

Describe the issue or problem
The registration emails and review requests are not being sent to reviewers who are using public domain email addresses such as Gmail, Hotmail, and Yahoo. However, other email addresses normally receive the registration email and review request.

Steps I took leading up to the issue
We noticed that the system normally confirms that the reviewers were notified, but when we contacted the reviewers manually, they told us that they did not receive the registration email or the review request. So, we have tested sending the emails using a Test paper and we concluded that all the emails to Gmail, Yahoo, and Hotmail accounts were not sent. Could you please give me a hint of why this problem occurs so that I can resolve it?

What application are you using?
OJS 3.4.0.8

Additional information
Please add any screenshots, logs or other information we can use to investigate this problem.

Hi @Mohamed_Abdelrazek,

As a starting point, I would recommend reviewing the deployment and troubleshooting recommendations found here: https://docs.pkp.sfu.ca/admin-guide/en/deploy-email

If you look at your logs as well and are able to find specific problems, feel free to share them here on the thread.

-Roger
PKP Team