What should I do if Mail on Mac OS 10.7.5 says "Missing plugin"?

Question

macOS

I mistakenly installed the "Universal Mailer" plug-in on Mac OS 10.7.5 with the wrong version (2.1.5 instead of 1.4). And now, when sending a letter, when you insert any attachment, the message "Missing plugin" is written. After installing the correct version of the plugin, nothing has changed, except for the plugin settings section in Mail itself. I deleted the contents of the Mail folder in the /Library/Mail directory, I tried it under a different account - it's still the same. Plugin version 1.4 is installed in ~/Library/Mail. What else can be done?