Send copy to field is limited to 255 characters

Hi,
one mail user need to send mail copy to 10 mailboxes at once but the "Send copy to" field in mailbox configuration is limited to 255 characters. Is there some good reason for this limit or is it possibility to increase the limit? I cannot use the "custom rules" option because mail user has to be able to set this field.
Thank you

 

I think this is not the best way to do this. I would use mail forwards instead.

 

Thank you. It works