If you're not satisfied with the provided mail methods (want a vm
one?), you can provide your own, more or less (patches welcome if you do
so). Here's what to do: set your :mail-method project option to,
say, foo, and write your own function which must be named
patcher-mail-foo.
This function must take two arguments (a project descriptor and a string containing the subject of the message), and prepare a mail buffer. If you want to do this, you should see how it's done for the built-in methods.
Note that the mail adaptation facility won't be available for your custom method. For that, you would have to hack the internals of Patcher.