NOT ABLE TO SEND EMAIL TO <.GMAIL> FROM <OUTLOOK 2007> , [MESSAGE ID HEADER ISSUE]

Pls find the below details of the case
1. We have the domain registered from Godaddy .
2. The website of this domain is on some other server & that is done by pointing A/CNAME records [Working Fine]
3. The Blog Website is on some other server & that is done by pointing A records [Working Fine]
4. An application is there which Rests on AMAZON AWS & NETLIFY Servers & that is done by pointing A/CNAME records [Working Fine]
5. The Current Email works on Google Workspace & we have pointed it by using MX Records [Working Fine]

NOW BELOW IS THE ISSUE

1. We want to migrate Emails from Google Workspace --- Hostgator Emails
2. We have purchased Hostgator Yearly plan which consists an unlimited Emails
3. Then we have pointed on Hostgator server by using A Records & MX records [ As told to us by Hostgator tutorial]
4. Then we have Tested the Hostgator Webmail UI <for the SEND/RECEIVE of Email> , it is working Fine.
5. Then we have configured Outlook client 2007 using the Hostgator details <For External client configuration>
6. Here the issue Comes as below
a. RECEIVING EMAILS : The Outlook Client was successfully receiving Emails
b. SENDING EMAIL : The outlook client is not able to send Emails to ANY <dot>gmail domain, as the error is occurring <Mentioned in Attached Files>