Exchange 2010 Couldn't connect to the source mailbox

So I was working on decomissioning a horribly broken and misconfigured SBS 2011 server today. Part of this was to export all of the mailboxes to PST and import on the new server (don't ask why but the customer had two SBS 2011 servers). When attempting to export a mailbox, i ran into this error:

Couldn't connect to the source mailbox.
    + CategoryInfo          : NotSpecified: (0:Int32) [New-MailboxExportRequest], RemotePermanentException
    + FullyQualifiedErrorId : CA71126,Microsoft.Exchange.Management.RecipientTasks.NewMailboxExportRequest

Well that's fun, so i re-ran the export command with -Verbose and ended up with:

New-MailboxExportRequest : Couldn't connect to the source mailbox. -->
MapiExceptionCallFailed: Unable to make connection to the server. (hr=0x80004005, ec=1249)
Diagnostic context:
    Lid: 59431   EMSMDB.EcDoConnectEx called [length=154]
    Lid: 34855   EMSMDB.EcDoConnectEx returned [ec=0x4E1][length=56][latency=0]
    Lid: 59505   StoreEc: 0x4E1
    Lid: 52465   StoreEc: 0x4E1
    Lid: 60065
    Lid: 33777   StoreEc: 0x4E1
    Lid: 59805
    Lid: 52209   StoreEc: 0x4E1
    Lid: 56583
    Lid: 52487   StoreEc: 0x4E1
    Lid: 19778
    Lid: 27970   StoreEc: 0x4E1
    Lid: 17730
    Lid: 25922   StoreEc: 0x4E1

After a bit of googling i did find someone else with a similar error, but their solution actually worked oppositely for me, so here is what i did to resolve:

Set-CASMailbox jsmith -MAPIBlockOutlookNonCachedMode:$false

After that, the mailbox exported correctly. I can't say for sure why this was blocked in the first place, but this did resolve it.