Did you include the encryption module in your project?
Did you try “clean deployment folder”, then “deploy for eclipse” and run project?
I hope this helps.
This appears to be a bug in the latest release: 5.0.1. Can you use version 5.0.0?
You could also use 5.0.1 and copy the EmailHandler.java file into the actions directory.
That file is available here: https://raw.githubusercontent.com/mendix/IMAPModule/master/javasource/imap_pop3_email/actions/EmailHandler.java
A new version that conains this file will be released soon.
This issue has been fixed in version 5.0.2 of the module.