The #imgx# tag doesn’t resolve to image

Using WP4.6.1, latest Postie version. Have message type set to text.

Message text includes something like this paragraph, and here is the image #img1# and some more text.

The images are sent as attachments.

The #img1# text appears in the processed email (in the post). How to get the #img1# text replaced with the actual image that was attached to the email?

Thanks.