Configure email forwarding with MS365 mailboxes

1. Configure email forwarding

It is possible to set up an email transfer with an Exchange Online mailbox to an external SMTP address from the adminstration portal https://admin.microsoft.com.

The mail transfer works without problem, because unlike the default configuration of Exchange On-premise, the mail transfer is allowed by default on the remote domains default policy.

2. Configure antispam to avoid error 550 5.7.520

However, sometimes internal mailboxes cannot send emails to the mailbox that is configured with an email transfer.

The error message is as follows:

Remote Server returned ‘550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS (7555)’

To correct this problem, access to the anti-spam configuration page of MS365 using the following URL:

https://protection.microsoft.com/antipsam

You have to look at the configuration of the “Outbound spam filter policy”.

Depending on your tenant configuration, multiple interfaces may appear:

To correct the problem, one solution is to set up the “Automatic forwaring” setting into “On – Forwarding is enabled.”

The mall transfer will then be functional as well for emails coming from external senders and from internal senders.