Office 365 dual delivery to Gmail setup

Hi David,

To resolve this issue, Please create a mail contact for your external ID and enable forwarding from O365 mailbox


and if you want to do it from Exchange Online PowerShell, Please do run below  command

New-MailContact -Name "David-GmailForward" -ExternalEmailAddress "ExternalGmailAddress"
Set-Mailbox -Identity “O365MailboxEmailID” -DeliverToMailboxAndForward $true -ForwardingAddress "ExternalGmailAddress"

Thanks Rohit, Unfortunately this won't work for my scenario as the email address is the same for both Office 365 and Gmail.  I should explain more: I am currently using Office 365 for the primary email server, but I also want to use the same email address with a new GSuite account I have setup, so I can switch between GSuite and O365 depending on what I need to do.  In GSuite I have validated the domain and setup the email address, but I haven't pointed the MX record for the domain to GSuite, I have left it with O365. But I still want emails to appear in both O365 and GSuite.

There is a GSuite article about it: https://support.google.com/a/answer/9228551?hl=en - see the section "Legacy server as primary server" - I'm just trying to setup the "Set up server-based forwarding from your legacy server to Google." part of it.

I hope that's clearer. Thanks.

This is called shared smtp name space scenario and mail will get delivered to any one place only unless you add another domain in g suite and set forwarding to that domain at O365 side
Because email relay is not possible for single email address as source and destination both are same in this case

Thanks Mahesh, are you saying it's not possible to do what I'm trying to achieve?

If it is possible, can you give me some idea of how to go about it?

Thanks

Yes you are right

The alternative is like i said above

How this setup actually works like:
At gmail side setup. Onmicrosoft.com forwarders so that gmail users can send email to O365 users and at O365 side set domain to internal relay with connector which land from O365 to gmail so that if mailbox is not available at O365, the mail will get forwarded to gmail through connector

In any case user should be allowed to access any one mailbox

Hi Mahesh, the problem with that setup suggestion is that the mailbox will be available in O365, but I still want a copy to be sent to gmail through the connector.  I've tried various methods of setting up a connector to forward, but so far nothing works.

Hi Mahesh. I understand now, thanks for your help.