For anyone having trouble with "PHPMAILER" or "Could not instantiate" errors, be sure to try the "Set the sender to the default Joomla email address" option in the Control Panel. After an hour of wrestling with it because my host blocks email from non-local domains for security reasons, that option solved everything.
Fantastic module, I highly recommend it.
I do have one minor suggestion. My posts were appearing in the incorrect order within their month. This was because I did some hand importing of blog posts from another site. When I did this, they didn't all go into Joomla in the same order that they were posted. So my content.IDs were sort of in random order, then I went back and modified the content.Created date so it matched the original blog posting date.
The query in helper.php is "ORDER BY id" and I just changed it to "ORDER BY created" and now everything shows up the way I want it. The Order By option on the module itself only appears to affect the filtering for building the tree for display, and not the order of the queried items. The query should probably use that option as well.