The following script works fine in High Sierra but fails to attach files to the Mail message in Mojave. The message title, content and recipient are set correctly, but not the attachment. Any ideas?
---
set theAttachment to (choose file with prompt "Select file for attachment...")
tell application "Mail"
set theMessage to make new outgoing message with properties {visible:true, subject:"File Attachment Test", content:"Some test content" & linefeed & linefeed}
tell theMessage
make new to recipient at end of to recipients with properties {name:"John Doe", address:"johndoe@domain.com"}
end tell
tell content of theMessage
make new attachment with properties {file name:theAttachment} at after last paragraph
end tell
end tell