MailManager has a couple of useful test templates, "GenerateMail"
and "test", that are pretty much secret, although "GenerateMail" is
menioned in the README. "GenerateMail" is useful for putting mail
into the system if you don't care about the content of the mail, while
"test" allows you to import the raw text of a single message.
"test" is very useful and would be better with a select box for available
accounts and the choice of file upload as well as a text area.
Since these are useful features perhaps there should be links to them
from the front page.