The domain is missing in the emails when using TYPO3 9? Then you need to add the domain in the site-configuration!
The mode unsubscribeMode=1 works only if unsubscribeUid is set.
Since version 5.x there is not only one plugin name (pi1). In some cases therefore you need to change the template and add, modify or delete the pi-parameter at a f:link.external or f:form.
Since version 5.x the email content will not be translated when settings.email.dontAppendL=1 is set.
A bug tracker is available for this project at GitHub.