Category Archives: Office365

MigrationTransientException: Target database GUID cannot be used (Mailbox database size limits in Exchange Online)

If you are designing Exchange 2016 (or have been designing Exchange 2013) environment you are aware of the The Exchange 2016 Preferred Architecture (https://blogs.technet.microsoft.com/exchange/2015/10/12/the-exchange-2016-preferred-architecture/) and articles like Ask the Perf Guy: How big is too BIG? (https://blogs.technet.microsoft.com/exchange/2015/06/19/ask-the-perf-guy-how-big-is-too-big/) which explain pretty much how to design an Exchange solid (and large) Exchange environment.

When it comes to Mailbox databases, the recommended size limit for non-replicated databases is 200GB and for replicated databases 2 TB (when running 3 or 4 copies of a Mailbox database).

One can only guess how Microsoft has designed their Exchange servers in Exchange Online, but we can assume that the Preferred Architecture is written with their Exchange Online experiences in mind.

Sometimes error messages that are generated in Exchange Online can reveal more information. While moving mailboxes from Exchange 2010 to Exchange Online in a hybrid configuration the following error message was returned in a migration batch for a number of Mailbox databases:

Error: MigrationTransientException: Target database ‎’07bdf507-ab94-479b-aeb6-1bfef1458c4c‎’ cannot be used: Current database file size: 1502835900416 Current space available inside database: 100237312 Allowed database growth percentage: 90 Maximum database file size limit: 1622722691784 Is database excluded from provisioning: ‎’False‎’. –> Target database ‎’07bdf507-ab94-479b-aeb6-1bfef1458c4c‎’ cannot be used: Current database file size: 1502835900416 Current space available inside database: 100237312 Allowed database growth percentage: 90 Maximum database file size limit: 1622722691784 Is database excluded from provisioning: ‎’False‎’.

Obviously it’s telling us the migration cannot proceed since the target Mailbox (in Exchange Online!) has reached its size limit. The following sizes are reported:

  • Current database file size: 1502835900416 (1,502,835,900,416 bytes, approx. 1.5TB)
  • Current space available inside database: 100237312 (100.237.312 bytes, approx. 100MB)
  • Maximum database file size limit: 1622722691784 (1.622.722.691.784 bytes, approx. 1.6 TB)

So, the maximum size limit for Exchange 2016 in Exchange is not really used in Exchange Online, but it’s getting close, which is interesting to see.

What I don’t understand is why this issue occurs in the first place. To me it looks like a failing part in the provisioning service but I have to admit I’ve never seen this before in the last couple of years so I expect it’s only one Exchange server that’s failing here.

Exchange Online PowerShell multi factor authentication (MFA)

It’s a good thing to enable multi-factor authentication (MFA) for Office 365 administrators. For web based management portals this is not a problem, just enter your username and password, wait for the text message to arrive, enter it in the additional dialog box and you’re in.

For PowerShell this has been more difficult, but MFA for PowerShell is available as well for some time now. When you login to the Exchange Admin Center and select hybrid in the navigation pane you can configure a hybrid environment (first option) or install and configure the Exchange Online PowerShell MFA module.

Click on the second configure button, and in the pop-up box that appears click Open to start the installation of the PowerShell module:

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Continue reading Exchange Online PowerShell multi factor authentication (MFA)

Disable automatic forwarding in Office 365

By default automatic forwarding and automatic replies of email messages is turned on in Exchange Online (Office 365). You can turn this of in the Exchange Admin Center of Exchange Online (https://outlook.office.com/ecp).

Logon using your tenant administrator, select mail flow in the navigation menu and select the remote domains tab.

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Open the Default remote domain and deselect the Allow automatic replies and Allow automatic forwarding checkboxes under Automatic replies.

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When you click Save automatic forwarding and automatic replies will be turned off in your Office 365 tenant. Please be aware that it can take some time before the settings becomes active (I think due to replication issue).

DKIM in Office 365

Microsoft has implemented DKIM, DMARC and SPF in Exchange Online, the only thing you have to do is enable it. The only thing for DKIM you have to do is create two CNAME records in DNS and enable DKIM in the Exchange Admin Center.

DKIM CNAME records

The CNAME records you have to create for DKIM look like this:

selector1._domainkey.contoso.com
selector2._domainkey.contoso.com

Selector1 and selector 2 are the 2 selector tags (in Office 365 these will always be selector1 and selector2), the _domainkey is a default tag that will be added. Of course you have to replace the contoso.com with your own domain.

The CNAME records have to point to the following locations:

selector1-contoso-com._domainkey.contoso.onmicrosoft.com
selector2-contoso-com._domainkey.contoso.onmicrosoft.com

Continue reading DKIM in Office 365

412 Cookies are disabled

This blogpost is more a note to self, but sigh, I hate it when it does this…. show the 412 Cookies are Disabled error message when trying to open the Exchange Admin Center (EAC) in Exchange Online:

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I’m not sure if this issue shows up every time, but at least it shows up when you want to configure an Exchange Hybrid Configuration and you select Hybrid in the On-Premises EAC and select Sign In to Office 365.

To solve this, select the Tools menu in Internet Explorer, select Internet Options and click the Privacy tab.

Lower the slider just one click to Low and click Apply or OK.

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Now when you refresh the page in Internet Explorer it should continue with the Hybrid Configuration page:

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