You can follow the steps below to setup your custom email on your phone/device using the Gmail App
1. Open your Gmail app and click on Add another Account
2. Click on Other
3. Enter your email and click on Manual setup, then click Next
4. Choose IMAP
5. Enter your email password and click on Next
6. In the server field, type mail.yourdomain.com and click Next
7. Edit the SMTP server to mail.yourdomain.com and tick the require signin option, then click on next
8. If the network is okay and password is correct, and all went well, it will come to this page, then click on Next. That is all
9. Enter your name and click Next. That is all
