Amazon SES custom mail from while using Workspace

What this means, is if you setup a custom mail from domain, lets say mail.example.com you need to publish a single MX record in the example.com DNS zone, called mail that points to 10 feedback-smtp.region.amazonses.com (where you replace region with the AWS region that your SES identity is configured in.

What you have written in bold isn't 100% correct specifically "you must publish exactly one MX record to the DNS server of your MAIL FROM domain." is incorrect. MX records are short for "mail-exchanger" records. They tell an email sender on the internet, where to send email for your domain.

When an email is sent, it has two addresses that indicate its source: a From address that's displayed to the message recipient, and a MAIL FROM address that indicates where the message originated. The MAIL FROM address is sometimes called the envelope sender, envelope from, bounce address, or Return Path address. Mail servers use the MAIL FROM address to return bounce messages and other error notifications. The MAIL FROM address is usually only viewable by recipients if they view the source code for the message.

If you configure a custom mail-from then SES will set the envelop sender to that address. The MX record is there so that a recipient knows which host on the internet to to send a bounce and other error messages.

Getting back to your question about G-Suite. If you are sending email from gsuite with a from address of user@example.com, then whatever G-Suite sets as the mail-from will apply, that may be different to the one you set with SES.

If SES sends an email from user@example.com it will set the mail-from to mail.example.com or whatever you configured it to be. They can co-exist.

The only criteria is that in SES your mail-from must be a sub-domain of the verfied identiy domain that you are sending from. If you set your mail-from to mail.example.com then you must send e-mail from @example.com

Last issue, if you send mail with addresses in example.com such as user@example.com from both SES and Gsuite, you need to make sure that the SPF record that you define - designates both SES and Gsuite's outgoing servers as authorized to send mail on behalf of example.com else some of them may bounce.