Postix - Open source email server for Unix, IBM Public license.
Postfix Add Mailbox
1) Login to Postfix. e.g. https://mail.opensourceecology.de/
2) Choose "Add Mailbox" from the main page
3) Enter the mailbox data
Email sent! The mailbox has been added to the mailbox table, but none (or only some) of the predefined sub-folders could be created.
Receiving and sending emails with Thunderbird works.