Email sending failed

I just upgraded to Manager 16.3.54. and now email sending is failed again and again.
i have looked in email setting for smtp but still my problem is not solved

I’m not seeing any new issues with email on my systems.

Are you using a custom SMTP server? If so, is testing the settings successful?

What messages or errors are you seeing specifically?
And what operating system are you using?

Email sending is now okay by changing my port setting from 465 to 25 for
Thanks for support and replies.