https://tamrindarkhane.com: Post SMTP email error

You getting this message because an error detected while delivered your email.
For the domain: https://tamrindarkhane.com
The log to paste when you open a support issue:
The mail server could not deliver mail to mahyar.moazzeni@gmail.com. The
account or domain may not exist, they may be blacklisted, or missing the
proper dns entries.