postie create empty “tmpTitle” post when email has attachment

Hi, I have been using postie to automatically create page for a few years. After updating postie to the latest version about a month ago along with many other plugins, I noticed that, if the email has an attachment (pdf file, text file), even the attached file is very small (<1 MB), postie will create an empty “tmpTitle” post. As soon as I remove the attachment from the same email, postie will work correctly, and create a page.

I searched the forum, looks that this question has been asked many times before, and after the users installed “add-on” from postie. All original posts were closed without giving a definitive answer to what causes this issue.

It will help other to trouble shoot the issue, and list the potential causes after it is solved. So that the same will not be asked over and over again.