sendmail, rails and spam

We're having a terrible problem with sending email using sendmail and rails.

We believe we have everything set up correctly. (I've changed the domain name below because this is so embarrassing ). Our mail config looks like

ActionMailer::Base.delivery_method = :sendmail ActionMailer::Base.sendmail_settings = {   :location => '/usr/sbin/sendmail',   :arguments => '-i -t -f support@oursite.com' }

our notifications look like

    @from = "oursite <support@oursite.com>"     headers "Reply-to" => "support@oursite.com"

and we have an SPF record that resolves back to your one and only server. EMails are making it into gmail, fine, no problem, but are getting flagged as spam in Yahoo and are not even making it into Hotmail (which is crazy because my old hotmail account has around 2000+ new messages in the inbox 99% of which are spam, and 11 in the spam folder, 2 of which are legit).

This may be off topic but I'm just stumped, and I'm not smart enough to work this out on my own. Does anyone have any suggestions on how to get this working or an alternative method (we're using Slicehost for hosting if that make a difference).

Thanks in advance Dale

(Salty)Pete -

Thanks Jodi, we'll give this a try and see if it works