Migrate email accounts and forwardings

[landauf]

The email accounts (including all stored emails) and all email forwardings should be migrated to the new server.

The migration should happen in an "atomic" step, i.e. it shouln't be possible that mails are still received on the old server AFTER the accounts were migrated because that would result in a loss of data.

Loss of data should be avoided in general. It is however acceptable if the email accounts are unavailable for some hours.

[lferran]

• I assume that the migration of stored emails only applies for users that we migrated (Tickets 8 and 29) that had a <user>@orxonox.net mailbox in the old server.

[lferran]

@landauf: do you know how are email redirects configured in the old server? We should fetch them, and re-configure them in LDAP.

[lferran]

The above issue has been fixed in ticket:480