Postfix with AMAVISD how to white list

[Jason Hirsh]

I have blocked files with gif attachments to block that category of  
spam.

I do however have some people who send me legitimate gif attachments
I tried to white list them by adding

@whitelist_sender_maps = ( ['.example.org', '.example.net'] );


to amavisd.conf but exampl.net continues to get bounced with bad  
attachments.

Any ideas where I can look for a solution??