Tenant to tenant email redirection during divestment

somnio 1 Reputation point
2021-10-07T22:37:01.577+00:00

Hi all,
firstly, is this possible?

Tenant 1: Contoso.com
Tenant 2: Tailspin.com <divestment of contoso.com>

During migration the following scenario will occur. Any email to dave@tailspin.com needs to be redirected to dave@Company portal .com, until the mailbox is migrated to tailspin. There are ~5500 mailboxes to migrate

We have tried these transport rules:
Recipient is a member of MESG -> redirect to connector "TS to Contoso". Where the MESG contains dave@tailspin.com mail enabled contact.
sender is a member of MESG -> redirect to connector "TS to Contoso". Where the MESG contains dave@tailspin.com mail enabled contact.
Message is to a member of MESG -> redirect to connector "TS to Contoso". Where the MESG contains dave@tailspin.com mail enabled contact.

The connector "TS to Contoso" is verified

so far we get really intermittent success ranging from delivery taking 1-4hrs to NDR's of "sent to the wrong region" or "too many hops - possible loop detected"

MESG = Mail Enabled Security Group

Many thanks for your thoughts and advice

Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Joyce Shen - MSFT 16,651 Reputation points
    2021-10-08T02:49:07.127+00:00

    Hi @somnio

    Please correct me if I have any misunderstanding about your description, do you mean the users are migrating from contoso.com to tailspin.com and you want the mails sent to tailspin.com redirect to contoso.com?

    Which migration method are you using? What's the recipient type of the account 'dave@tailspin.com' ?

    We could refer to the methods list in the official document Control automatic external email forwarding in Microsoft 365. To see if any other solution can be used in your scenario.

    In addition, for this error: "too many hops - possible loop detected"
    For example, if a user has two accounts, forwarding to each other, it may results to an endless loop. A message sent to User1 account is forwarded to another mailbox; if that mailbox account is set to forward to User1, then a mail loop is created: mail goes from User1 to the mailbox, back to User1 and then back to the mailbox again, etc., until the loop is ascertained and the message returned to its sender.

    You may try changing the mailflow condition, or make Stop processing more rules is checked on the rules to avoid the loop.
    Mail flow rule conditions and exceptions (predicates) in Exchange Online
    How to migrate mailboxes from one Microsoft 365 or Office 365 organization to another


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