Are the mail filters processed at the time email is received (on the server) or at the time they're viewed (by the client)?

To be more clear, as an example, let's say that I set up some filters using the Zoho web client that move certain emails to different folders based upon the sender's email address.  Then, let's say I later access my email account using a third-party IMAP client (e.g. Outlook) after some emails matching the filters had been received.  Would the third-party IMAP client "see" these new emails in the correct directories or would the new emails not be moved until I access my account using a Zoho web client?

Related, what are the limits on the number/complexity of filters? 

That is, if I have a large number of email addresses I want to match and route to the same folder, would it be more efficient to have one large complex rule ("Any of these conditions" with a large number of "From" conditions) OR would a large number of single-rule filters, one for each email address, be more efficient?

Thanks in advance!