Not a valid email address because it is not of the form user@host
From MozillaZine Knowledge Base
- This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).
This error message can occur if you're trying to use email addresses without a domain such as <lastname.firstname> on a corporate internet. Thunderbird expects the full email address.
A workaround is to use the Allow Local Addresses extension.
