i use the spam option for my mails since 4-5 weeks and I have only one problem. Sometimes, mail in my whitelist go into spam.
For example, I have email@example.com into my whitelist. I could receive like 5 mails a day from this services and I always have 1-2 mails that goes into spam. It's not supposed to go into spam, cause the whitelist should be checked before a possible spam calculation.