Partial SBS to Exchange Online migration

1) Export emails from current SBS account.
2) validate domain on Exchange online, add TXT record in public DNS and verify the domain in O365 and make as primary.
3) Create new users in cloud and assign license which will provision a new mailbox in cloud for the users.
4) Import Exported Emails in to the mailboxes.
5) convert exchange 2010 mailboxes to mail-enabled users.
Reference Article (Applies to all)- https://docs.microsoft.com/en-us/exchange/mailbox-migration/perform-a-staged-migration/convert-exchange-2007-mailboxes
6) force update of Global distribution list (How?) Office 365 does not work as exchange server so there is no need for updating GAL. Office 365 is online so GAL is online available always.
Hide mailboxes from Exchange global address list which are excluded from migration.
7) Configure your MX record to point to Office365.
8) Create an Autodiscover and other DNS records.
9) Login into OWA for user in cloud after mx pointing and ensure internal and external mail flow.
10) setup new accounts in new Outlook profiles and mobile devices
11) Stop and disable on premises Exchange services for a week and verify office 365 functionality.


In general, it’s not recommended to uninstall the Exchange Server(on-premises ) from SBS, due to everything integrates with each other tightly. And Microsoft official documents/KBs have mentioned some known issues.

However, since you have migrate Exchange server to O365, and if local Exchange server is no longer to use, you may try to remove it. Below links are for your reference, it is better to make a plan and test it on VM/non-product environment before any change on your SBS environment.

How and when to decommission your on-premises Exchange servers in a hybrid deployment:
https://technet.microsoft.com/en-us/library/dn931280(v=exchg.150).aspx

Uninstall Exchange Server:
https://technet.microsoft.com/en-us/library/dd728003(v=ws.10).aspx

Please see my comments below.

1) Export emails from current SBS account. OK
2) validate domain on Exchange online, add TXT record in public DNS and verify the domain in O365 and make as primary. OK
3) Create new users in cloud and assign license which will provision a new mailbox in cloud for the users. OK
4) Import Exported Emails in to the mailboxes. OK
5) convert exchange 2010 mailboxes to mail-enabled users. Is this necessary? I've seen others just disable the local mailbox
Reference Article (Applies to all)- https://docs.microsoft.com/en-us/exchange/mailbox-migration/perform-a-staged-migration/convert-exchange-2007-mailboxes
6) force update of Global distribution list (How?) Office 365 does not work as exchange server so there is no need for updating GAL. Office 365 is online so GAL is online available always. I meant the SBS GDL. To remove the users that have been migrated. The SBS will keep working until they decide to complete the migration for the other two domains.
Hide mailboxes from Exchange global address list which are excluded from migration. If I disable the mailboxes and figure out how to force the update of the GAL, will they not be removed from the SBS?
7) Configure your MX record to point to Office365. OK
8) Create an Autodiscover and other DNS records. OK
9) Login into OWA for user in cloud after mx pointing and ensure internal and external mail flow. Here is where I had issues before. I could send email to the Cloud account and receive email, but the rest of the SBS users couldn't send email to them
10) setup new accounts in new Outlook profiles and mobile devices OK
11) Stop and disable on premises Exchange services for a week and verify office 365 functionality. Not going to happen yet

This is the error that I received when I tried to send from an SBS user to the Cloud after I made the whole change and disabled the SBS mailboxes

Diagnostic information for administrators:
Generating server: SBSSERVER2011.local
IMCEAEX-_O=DOMAIN_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT+29_CN=RECIPIENTS_CN=user@domain3.com
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

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This is the error that I received when I tried to send from an SBS user to the Cloud after I made the whole change and disabled the SBS mailboxes:

If you want to use co-existence in SBS is not possible. Since MX is pointed now to Office 365 and mailboxes disabled when sending email from on-premise SBS it will not find the user and you will get error:

#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

You will have to use the cutover method as decribed above and convert these mailboxes to mail-enabled users for it to work.

But in cutover migration you will have to use a batch.

The migration you are doing is straight forward where you cannot send mail from SBS. You can only do it in Office 365 for migrated mailboxes.

If you want co-existence then you will have to setup hybrid setup.

In SBS hybrid setup is not gonna work, you will have do cutover migration.

Even if the other two domains handled by the SBS are not changed?

Company1 - mx/DNS records to SBS
Company2 - mx/DNS records to SBS
Company3 - mx/DNS records to Cloud

Company1 - mx/DNS records to SBS
Company2 - mx/DNS records to SBS
Company3 - mx/DNS records to Cloud

This kind of migration where you only want to migrate one domain after one domain is called as hybrid so even if you keep mx for one domain pointing to Office 365 and would need to have send email from another domain user send an email to Office 365 migrated domain is called as hybrod setup.

So why are we converting  exchange 2010 mailboxes to mail-enabled users is to let exchange know that the users are now in cloud and these mailbox will have a target address stamped after convertion.

But since this an SBS server and you could not setup hybrid in it that only option is to go for a cutover migration and migrate all domain at once.

Just to understand a bit better. In order to achieve what I want to do, I have to go through the process in step 5, which basically allows local messages to be delivered to local mailbox and then forwarded to the cloud?

When I hear cutover migration, I think that I should migrate the whole SBS to the cloud, which is not what the end user wants at the moment. They want to test the cloud setup with one of their smaller domains and then move the rest.

Sorry for the seemingly stupid questions but I've never attempted something like this and I don't want to mess it up. I can setup O365 from scratch or migrate from POP3 accounts, but I've never had to deal with Exchange to O365.

Yes go through step 5 and see the difference.

Thank you. I will attempt this once all three users are back from their business trip. Is there a way to revert the changes to the mailbox if something goes wrong?

So lets say you converted the mailbox to mail enabled user.

You can revert the change by running command:

Get-Mailuser “Joe TestUser” | Enable-Mailbox -Database EXCHDB01