How do I fix this: master: Warning: fd limit (ulimit -n) is lower than required

[Robert Chalmers]

I get this when I reload dovecot after any changes. How can I fix it? I can’t 
find any reference to it anywhere.


master: Warning: fd limit (ulimit -n) is lower than required under max. load 
(256 < 1000), because of default_client_limit

thanks
Robert