emails from gmail to secondary email address not being received

emails from gmail to secondary email address not being received

I've been experimenting with sending emails to my secondary email address, and I've found that they are being received when sent from a hotmail account, but emails from gmail to my secondary email address are not being received, as summarised below:

                             to
from            primary       secondary
----------------------------------------------------------
gmail:             ok                  not ok

hotmail:          o k                     ok


Any idea what's happening here?

Thanks

Jason