Dealing with annoying spammers using my domain in their From

Is there a regex that matches the following?

* ^TO(_dot_)*(_at_)elastica(_dot_)com
* !^TO(robert|ann)@elastica.com
$BOUNCES

The idea is to capture any emails that don't use robert or ann but use 
@elastica.com
Spammers are using my domain in their From and I'm getting all their 
bounces.

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