I post to Posterous, Tumblr and WordPress by email. Lately, my posts have been showing up everywhere but Tumblr. I did a few tests, and discovered that posts show up on Tumblr ONLY if I list it *first* in the “To:” box of my email. I have no idea why it works this way, but it does. If anyone else has been having this problem, try this yourself and see if it helps.
Figured out Tumblr “post by email” problem – Tumblr wants to be first in line