There is a workaround for the passbolt mailserver configuration and a good reason behind it, you can see both here: https://www.reddit.com/r/passbolt/comments/uct0v1/comment/i6d7id6/
You can also use a free gmail account if you want the benefits of using passbolt with the mailserver configured without having to set up your own: https://help.passbolt.com/configure/email/smtp-authentication.html#google
Passbolt also has a variety of installation options other than a docker container: https://help.passbolt.com/hosting/install
I do work at passbolt. Just wanted to share this information in case it's helpful. Let me know if you have any questions or feedback.