I received a Sys/Temp error message -16999 could not retrieve mail using Entourage on my MacBook Pro. My account setting hadn't changed and my Internet service provider was no help. I was told that they don't support Entourage and could refer me to a paid service to help me with my problem. I did some online sleuthing, found several suggestions, one of which worked. I went to the Web mail version of my account, created a new folder and moved the first email in the queue from my inbox to said folder. I went back to Entourage, performed a send and receive and all my emails poured in. There was something wrong with that one email. No idea what, but I contacted the sender to resend it and I rec'd it without a problem.