All posts using default author

Every post I send through Postie is showing up as a post from admin. The debug log shows this odd behavior (obviously anonymized):

RemoveExtraCharactersInEmailAddress: <masked>@gmail.com (1)
ValidatePoster: post email filter <masked>@gmail.com
Confirming Access For <masked>@gmail.com
4 has 'post_via_postie' permissions
posting as user 4

Just beneath it, the script determines the id for the default user.

ValidatePoster: looking up default user admin
ValidatePoster: found user '1'

I would assume it would ignore this and use the poster ID, but further down, it reverts to the default:

Array
(
    [post_author] => 1
    [comment_author] => <masked>
    [comment_author_url] => http://<masked>
    [user_ID] => 4
    [email_author] => <masked>@gmail.com

Any ideas why it would be doing this? I can email the full debug log if needed.

http://ww.wp.xz.cn/extend/plugins/postie/