Regarding Spam to email ratio:
We like SpamStopsHere.

Basic setup is effective, and has many filtering options available.
You can block your own phrases and sources and Subject strings etc.

If you decide to try it we are a reseller, so may be able to offer value.
(Shameless plug, but may be helpful to someone).
We host email for a few hundred companies and have every one of them (including our own) is using this service, so we get a good rates.
Still it ain't cheap, but every company has seen the difference and continue to use us.

Now I've talked about email services for two posts in a row and just want to finish by saying; I hate email.
I hate supporting it even more. I train beginning techs for that so I don't have to. smile

Yesterday we had a user submit a help desk ticket stating her email login wasn't working and provided the credentials she was using. The tech logged in, sent himself an email and logged out. Told her the login was correct and her email was working. Could she please try again and report back in detail.

Today she submitted another help desk ticket asking us to turn off the forwarding she had set up last week before leaving, as she didn't know how.
Her email was working like it was supposed to .. it was set to be forwarding to another address and it took her a day to remember she had done this.
The problem was between the chair and the keyboard.

I do not work here, but the benefits are still awesome
Make your sound your own!