For me the solution also was: simply change the folder name from “welcome-email-editor” to “-welcome-email-editor” (adding “-” at the beginning) in the plugins folder (wp-content/plugins/-welcome-email-editor/).
1. I got the mistake in the “Plugin”-area (wp-admin interface)
2. Still activated the plugin (despite the mistake)
3. New users got correct e-mails
However, I DIDN’T rename the folder back to “welcome…” without “-“.
Hope that helps someone.
