Yesterday, AOL reported that they made a change to how they filter incoming email messages. Their spam filter has now been tightened so that they’ll issue more “CON:B1 Refuses” to mailers. CON:B1 blocks are caused by a spike in unfavorable email statistics.
When asked to clarify what AOL means by “unfavorable email statistics,” their Postmaster blogger, Lili Crowley, said that this encompasses filtering based on content, too many complaints and the percentage of invalid addresses on a list. She added that “if users complain about mail, then the mailing reputation of the sender can suffer. Invalid recipients and bad content also contribute.” AOL would not go deeper into specifics — it is rare for an ISP to spell out exactly what they are doing for fear that spammers will work their way around these new filters.
AOL acknowledged — even forewarned — that legitimate senders might be negatively impacted by these changes. If you find that your email isn’t going through due to this type of block, contact AOL’s Postmaster at http://postmaster.aol.com.
Of note here is that if your email is refused by AOL due to a CON:B1 block, it means that they view your email sending reputation as low. If that happens, there’s not a lot that your email service provider can do about getting your messages through to AOL’s inbox. Improving your sending reputation requires you to follow best practices, including keeping your list clean and sending relevant messages.
See MailerMailer’s Getting Started with Email Marketing guide for tips on what you can do to increase your chances of getting your messages delivered to your recipients’ inbox.