enable SSL or TLS authentication for email

Email Error: SMTP Error: The following recipients failed: clientname######################

Last week, all of a sudden, I kept receiving that error message while emailing from the admin for the whole day. Then the emails went through ok the next day. But I again received that error today.

My host told me that I needed to enable SSL or TLS authentication in my script.

I'm not sure about enabling SSL/TLS authentification but found the following info in the troubleshooting email problems:

... Mail requires that your email communications occur over a secure channel, which means you need to send on port 465 or 587, and with SSL/TLS. The latest version of Zen Cart supports this by using the following settings: Email Transport: SMTPAUTH
Email Linefeeds: LF
SMTP Username: your mail username
SMTP Password: your mail password
SMTP Host: smtp.yourdomain.com
SMTP Port 465 or 587

My port used to be 26. I changed it to port 465 and the emails now go through without any error message. But is this safe and the best option?

Another question is that my SMTP Host in the admin is currently mail.mydomain.com, should it be changed to smtp.mydomain.com?

Please advise

I'm not sure I understand your questions.

If you only changed the port from 26 to 465, that's fine ... that's needed by your mailserver setup.
And as far as the SMTP Host is concerned, you must use whatever address your host gives you to point to the right server where Zen Cart must connect in order to send emails. It could be "fred123.somedomain.com" if that's what they called it. Use what they tell you.

Thanks for confirming port 465 is fine.

They just advised to use smtp or smtpout, none of which work. So I will simply keep using mail, since now it works fine as is.