Advanced Forwarding Rule to exclude a sender?
 

How can I create a forward rule that will forward all messages to an email address except messages from a specific sender?

I know how to create advanced rules that when something is in a header, such as this:
allof(header :contains "from" "xxx.com", header :contains "to" "yyy@abc.com")

But I'm not sure of the syntax to exclude something.

Thanks for any help.

Just put " not " (in lower case) before " header " in any partial rule you want to negate.

A good summary of what you need to know to use sieve for most practical cases is at https://kb.vircom.com/redirfile.asp?id=581&SID=