I’ve checked the error log but I don’t see anything explicitly about error generated by the Postie plugin. I’m seeing this error — “Trying to get property of non-object in wp-content/themes/Divi 3.0/functions.php on line 8568” — repeating many times around the time I was trying to get the posting by mail function working again. The function in question handles the “overwrite_canonical_redirect”. I’m not familiar enough with the underbelly of WordPress to know what that actually means.
As I mentioned, my account it the administrator account. In the “Roles that can post” section, the administrator chechbox is ticked but I can’t select any other checkboxes (and save the results). Also, in the dropdown list for the default poster field, my account is the only one that shows up but the error message is still displayed even though it is a valid account.