Consumerist has a jpg of the actual letter, but the summary of it is:
AT&T DSL subscribers who use their ISP email will now have the pleasure of seeing ads in their email service. That they pay for. Did we say that already?
We're not sure whether this means ads will simply appear in the email interface or be inserted at the bottom of emails but reader Crayonshinobi is not happy.
Of the announcement that landed in his inbox this morning, he says, "I'm finding it ridiculous that all of our pay services now have to come bundled with advertising...and it was really slimily written too...until now, as a DSL subscriber, I received the non-ad supported webmail service, so by placing ads in my webmail, you've just removed services from me in effect...Thankfully, I use firefox with adblock...so if there are ads...I won't be seeing them anyway."
Complaints: AT&T DSL Downgrades Email, That You Pay For, To Include Ads - Consumerist