[Exim] exim 3 address rewriting

Is there a default rule in exim 3 to rewrite an email address and
change its domain if the email address bounces?

This is what the rewrite section in our config looks like:

# Rewrite

I.e., we have no rules specified, yet we get instances where an email
that was destined for randomuser@??? will wind up being sent
to randomuser@???. I have no idea how this is happening.
Could this have some thing to do with the retry rules?

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Gabriel Ricard
iMaxSales.net