Configured Email Server Settings (SMTP) from from admin panel through Customization/Config with mailgun as service provider. After inviting a member it showed "The invite has been sent to the user's email." but the email did not received and in backend there is a timeout error happening

Steps to reproduce the behaviour :

1. Go to '/admin/customization/config'
2. Configured Email Server Settings (SMTP) with mailgun as service provider (Authentication:Plain, Port:465)
3. Got to '/admin/member_manager/invitations/new' submit email address and it will show the email was sent
4. Go to the instance console of your cloud provider where the forem is hosted and hit 'journalctl -f -u forem-rails.service' there will be a timeout error
5. Error log :
   Error log.txt

Expected behaviour :
The email should receive

OS : Linux

Cloud Provider : AWS

Additional context :
Tried with Sendgrid and same timeout error is occurring, Changing port is not making any changes