Mail from WordPress is not being sent to certain email providers

We have a website that caters to users with memberships. Process flow of registration is as follows:

• User access and registers on Signup page (gravity forms registration)
• User pays for their membership
• Once payment is completed two emails are triggered (1) Activation Email, (2) Welcome email with password reset link

For gmail, registration is seamless. But for other email providers like outlook and yahoo. Activation email is not being sent out from wordpress.

Website is hosted on IONOS. We have WP SMTP Mail installed but its error is not being shown in logs. Our SMTP Host is IONOS as well.

Any help would be appreciated! We cannot currently track which emails are being sent and are not.

• This topic was modified 1 year, 2 months ago by Steven Stern (sterndata).