Set up MX Record to G Suite not working

Good day! I have followed this tutorial for setting up MX Records from G Suite - https://wiki.centos-webpanel.com/set-up-mx-records-for-g-suite-gmail

For the first 10 minutes, it worked but after a few hours, every email that I send to our sample user prompts

Code: [Select]

[b]Message not delivered[/b]

Your message couldn't be delivered to -----@------.com because the remote server is misconfigured. See the technical details below for more information.

The response from the remote server was:
554 5.7.1 <-----@------.com>: Relay access denied

But if I check our G Suite admin account, the status is fine

Code: [Select]

Verified -----------
Gmail is activated for -------

Should I delete all the CNAME bind for mail, pop, smtp, others? But the guide only dictates removing all the MX Record. Thank you