Alberto,
I asked what was the meaning of the "Database Error" message, and
Mike told me that those addresses were bouncing.
Wouldn't it be better to write that explicitly, instead of a generic
"Database Error" ?
I agree, it would be.
If you haven't already, you should reply to Mark about that. But I'll bet he's already on it, just from your question.
For what it is worth, Mark isn't a member of GMF, and wouldn't likely see a suggestion like that posted here. We're strictly user-to-user group for questions and advice. The official "suggestion box" for Groups.io is the beta group:
Shal
Shal Farley