Unable to connect or restore a SoftDeleted mailbox

Hi I need some help with connecting a SoftDeleted mailbox.

I have moved all mailboxes from one Exchange 2010 SP3 server to a new Exchange 2010 SP3 server in another forest.

I noticed in the logs that some mails have been discarded, because the limit for email sizes was smaller in the new forest.

I need to re-connect the mailboxes on the old server, to export the mailboxes to PST in case some important mails are missing.

I have done a Clean-MailboxDatabase, and I can see all the disconnected mailboxes. They are in the state "SoftDeleted".

When I try to connect them to a new or the same user, I get this error:

(New-MailboxRestore)

new-mailboxrestorerequest -sourcedatabase "Mailbox Database 0091415308" -SourceStoreMailbox John Doe" -TargetMailbox "John Doe"
This task does not support recipients of this type. The specified recipient John Doe is of type MailUser. Please make sure that this recipient matches the required recipient type for this task.+ CategoryInfo          : InvalidArgument: (John Doe:MailboxOrMailUserIdParameter) [New-MailboxRestoreRequest
   ], InvalidRecipientTypePermanentException+ FullyQualifiedErrorId : D1F70951,Microsoft.Exchange.Management.RecipientTasks.NewMailboxRestoreRequest

(Connect-Mailbox)

Connect-Mailbox -Identity "John Doe" -Database "Mailbox Database 0091415308" -User johndoe
Mailbox "John Doe" doesn't exist on database "Mailbox Database 0091415308".+ CategoryInfo          : NotSpecified: (John Doe:StoreMailboxIdParameter) [Connect-Mailbox], MdbAdminTaskExc
   eption+ FullyQualifiedErrorId : DEAB80D,Microsoft.Exchange.Management.MapiTasks.ConnectMailbox

(Connect-Mailbox to a newly created user)

Connect-Mailbox -Identity '797158d1-295d-45ee-8de1-e21aed609070' -Database 'Mailbox Database 0091415308' -User 'DOMAIN\NewJohnDoe' -Alias 'johndoe'
Mailbox "797158d1-295d-45ee-8de1-e21aed609070" doesn't exist on database "Mailbox Database 0091415308".