How to filter spam for a domain (third-party service)?

Question

Fight against spam

Hello. At the moment we are using the services of the Onlanta company
onlanta.ru/services/security/email , they provide this through the cisco iron port, but recently the quality ... in general, constant problems have begun: spam starts to pour in (weaken filters), then vice versa letters from clients do not come (they tighten the nuts), but here they have had some problems for a day and the mail arrives (if it arrives) with a delay of several hours, which is fundamentally unacceptable.
What are the options? Where to go? Who qualitatively filters spam and at the same time does not fall once a week? One of the goodies - storing mail on their server during the unavailability of their own - is a plus. Tell.

Answer 1

I use a bunch of CommuniGate + CGPCloudmark. Install a local client with black and white lists. But for large-scale projects, not a very good option.

Answer 2

Yandex .. spam does not come ..