Send Mail from a Custom Email Address with Gmail
To set up an email address for use with Gmail:
Custom Gmail From Addresses, ‘On Behalf of’ Tags and Sender Policy Framework
When you send mail from an address that is different from your main @gmail.com address through Gmail servers (instead of an external SMTP server set up for the address), Gmail adds your Gmail address in the email’s Sender header. If it can’t identify the settings based on your email address, manually input your SMTP settings, including the server and port, your username, and your password. Then, select Add Account. This procedure complies with sender-authentication schemes such as SPF. While the address in the From line may not specify Gmail as a valid origin, the Gmail Sender header makes sure the message does not raise red alerts for spam and fraud detection systems. Some recipients (those who use Outlook, for example) may see your message coming from “…@gmail.com; on behalf of…” when you send messages from your other email address.
