Trying to run New-MailboxExportRequest cmdlet on Exchange 2010 SP1 or later and getting following error.
The term ‘New-MailboxExportRequest’ is not recognized as the name of a cmdlet, function, script file, or operable program.

The most likely reason is that your user account doesn’t have Mailbox Import Export role. To add it run:

New-ManagementRoleAssignment -Role “Mailbox Import Export” –User domain\user.name

Restart Exchange Management Shell and you should be good to go.