#1, I have several types of accounts - each to be able to replicate what users we support experience and also to evaluate how to effectively deal with SPAM. As a provider, one of our products is managed messaging services, and we see a great many people who have corporate accounts that also have one or more either free, or low cost email accounts from MSN and Yahoo, or AOL.
Most use BYOA plans. We do measure and analyze SPAM patterns opposite various systems and filtration methods.
Our work has revealed that user behavior and the time an account has been active are the two biggest contributing factors regarding the amount of SPAM an account receives.
The longer an account of any type is in use, the more SPAM one will see - however, it is almost always the same type of SPAM and is easily managed with a combination of managed filters. The incidence of false positives is very low after a very short time.
User behaviors such as adult content access, online gambling, or warez site access result in the greatest amount of SPAM. Female users between 25 and 45 for example, see almost no SPAM. Males in the same age group will see 144% more SPAM and nearly half of it contains malicious code.
Paid Hotmail filtration is only better in one regard - more specifically identified addresses may be blocked. Free Hotmail's efficacy is just as high however.
Yahoo and AOL accounts are by far the worst - where the amount of SPAM renders the account nearly valueless. AOL 9.0 Security Edition BYOA versions offer some filtration, but it appears that AOL allows SPAM to come from paying senders. I cannot of course confirm that, but it certainly appears that way - owing to the reverse DNS lookups that AOL does and their application of rule #4 to the SPF.
Gmail accounts see very little SPAM if any. However, they are new and the addresses not well known. Specific tests with the same types of traffic that arrive from SPAM senders reflects that Gmail's anti-spam is ineffective.
The best combination we have found to stop nearly all SPAM is, RBL lookup at the edge,
GFI on mail servers, CVP Scanners at the edge and on each host (these kill mal-ware very well) and SPF (even on a low setting, SPF rule 4 can stop even the most persistent and clever SPAM techniques).
I'll say it again and again, "Give us our SPF and give it now - and yes, with Microsoft's connectoids and quarantine areas, please!" That'd kill all SPAM forever!
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