Hello TECHRECRUIT
The default domain for Office 365 users is onmicrosoft.com and it seems we are using CRM through Office365. Please go through the below steps for removing .onmicrosoft.com and using your own domain name:
1. Verify your custom domain on Office 365 by referring to Verify your domain and change name servers at any DNS hosting provider or domain registrar.
2. Click Add users, reset passwords, and more under users & groups in your Office 365 Admin Center.
2. Select your user name and click the pencil icon in the right part of the page.
3. In details section, under User name, click the drop-down list to choose the custom domain you have verified to replace the default onmicrosoft.com domain.
Please post back if you have any questions or concerns.
Regards,
Durgesh