How To Add Microsoft 365 Email Account to Gmail as Send Mail As

Gmail has a feature that lets you use Gmail to send emails from your other email addresses. For example, you own another email address like [email protected] and you want to send an email from that address right from your personal Gmail account.

It typically works like this:

• Email gets automatically forwarded from [email protected] to your Gmail account.
• When you reply to emails sent [email protected] you are using [email protected] instead of your Gmail address.
• When you send a new email in Gmail, you have the options to choose which email address to use as the sender.

To set it up, you basically go to the Gmail Accounts setting page, click Add another email address in the Send mail as section, and follow the instruction on the screen.

If you are adding a Microsoft 365 email account as another sender in Gmail, there are two main hurdles to overcome.

Microsoft 365 email auto-forward

The email auto-forwarding to an external email address used to be working out of the box, whether it’s set in the Outlook app level or the mail account level. But things have changed lately.

Now, external forwarding is disabled by default in Office 365. While usually it’s a good practice in general, it doesn’t help in this case. However, Microsoft still leaves a door open so you can change that if you need to, given that you understand the danger of it.

So, to re-enable external forwarding, go to the Anti-spam policy page on Microsoft 365 security page, and turn on Automatica forwarding under Outbound spam filter policy.

Enable SMTP Client Authentication

Again, Microsoft doesn’t mess around. The SMTP Authentication is disabled by default in Microsoft 365.

To disable, we need the help from PowerShell.

First, install ExchangePowerShell module if you haven’t done so.

Install-Module ExchangePowerShell

Then, connect to Exchange Online using

Connect-ExchangeOnline

And then, to enable SMTP client authentication, you need to enable it at organization level,

Set-TransportConfig -SmtpClientAuthenticationDisabled $false

as well as at the mailbox level,

Set-CASMailbox <MailboxIdentity> -SmtpClientAuthenticationDisabled $false

Once these two hurdles are solved, you can then move on to finish setting it up.