If you would like to send email from your domain name using your Gmail account please use the following steps:
Log into your Gmail account
Choose “Settings” from the right-hand corner.
On the settings screen there is a number of options, you will need to go to “Accounts”.
You will be taken to a screen where you have the option to “Send mail as".
Click on the blue "Add another email address you own" link. A modal window will now appear.
Add the name you wish your email address to come from in the "Name" field. For example, this could be your company name.
Add the email address you wish to email to appear sent from in the "Email" field.
Deselect the "Treat as an alias" tick box.
Click "Next Step".
Choose the "Send through Gmail" option and click "Next Step".
Click “Send verification”, you will then be asked to enter and verify the confirmation code, if you minimise this box and go back to your inbox you will have received an email which includes your confirmation code. Copy and paste this back into the window you have just minimised.
If you go back into “Settings” and “Accounts” you will be able to see next to the “Send mail as:” section the email address you previously entered will appear.
Hover over your new email address and click "Make Default".
You can now check this has been set up by choosing “Compose mail” and using the drop down box to select the email address you wish to send from.