SMTP Not working

Hello everyone, hope you are well.

I have two domains on my server and two email accounts for each. I set up SMTP accounts for each too. All needed ports are open on my LAN modem, and when I log in to Webmail for each email account through snappymail, I can send and receive email. However when I set the SMTP credentials for each email account to my domains’ SMTP config pages, and try to send email (like password reset etc), neither works.
I also have a domain hosted somewhere else, and when I set the SMTP credentials of that domain for my two domains here, both successfully send the emails through SMTP. However, my own email SMTP accounts don’t work for me.
Do you have any idea about the reason causing the issue?

I can send and recieve emails from snappymail; however, smtp is not working. Any help will be appreciated.

What is the results of checktls?

I have just checked on I have two screenshots below; one for the domain and the other for my statis IP.