Today, most of the e-mails I received from an Aweber list went to my Gmail SPAM folder. I marked them all as "Not SPAM", but this is the first time my Gmail account has marked messages from a reputable autoresponder as SPAM. Is Gmail just having technical issues, or have they started blacklisting legitimate autoresponder services?
Since it appears that you have not been experiencing similar things before, it might just be some technical issues.
Sometimes this happens if you are receiving a lot of emails from them. Gmail might think you are getting spammed and flag it as spam. Just go back in and keep marking them "not spam". Had the same thing happen today with another site.