There may be some grandfathering of old accounts: accounts that have email notification enabled, can still access the Packstation using mTAN transmitted by email. However, once the email notification is disabled, there seems to be no way to re-enable it (and maybe it is disabled per default for new accounts) [1]

[1] https://www.giga.de/tipp/dhl-mtan-anfordern-ohne-handy-das-s...