Hello,
Cisco IronPort has seen an increase in spam and other unwanted emails originating from IP addresses registered with and belonging to Yahoo! This spam originates mainly from Yahoo! Mail and Yahoo! Groups email addresses. This increase in spam has been reported by our customers through end user complaints as well as an increase in spam trap reports. The result has been a drop in the reputation of up to 5% of Yahoo’s IPs from good to the neutral range (between -2 and +1).
Cisco IronPort recommends that ESA customers throttle incoming connections from IPs with a neutral reputation score once the maximum number of connections has been reached. This results in Yahoo! IPs being throttled with the comment “Too many connections this hour”. Several customers have complained about not receiving emails from Yahoo! based not on Cisco IronPort intentionally blocking Yahoo’s IPs, but instead providing a reputation score based on the complaints we have seen and the threat of missed spam to our customers globally.
How can I avoid throttling Yahoo mail?
Cisco IronPort Email Security Appliance can be configured to not throttle mail by creating custom mail flow policies and sender groups for Yahoo domain mail servers (.yahoo.com).
More information on how to create custom mail flow policies and sender groups can be found in Cisco IronPort Email Security Appliance - Configuration guide (The Host Access Table (HAT): Sender Groups and Mail Flow Policies): http://www.cisco.com/web/ironport/index.html
Note: Accepting mail from domains or mail servers with low Senderbase reputation may lead to increase in missed Spam and potentially cause performance issues.
What steps has Cisco taken to help with this issue?
We have been communicating with the appropriate contacts at Yahoo! regarding their outbound mail issue and we have been assured that they’re working on it. Cisco IronPort has been providing Yahoo! with reports and any information that could help Yahoo! get to the bottom of this. While Yahoo! has told us that they are aware of this and are working on it, we do not have the specific details of steps Yahoo! has taken. We will continue to work with Yahoo! to help them resolve this issue.
Cisco IronPort has been actively updating rules numerous times a day against spam received from Yahoo! This should help against some of the missed spam issue if the customers were to take steps to accept all emails from Yahoo! and run IronPort AntiSpam on them. We request that customers continue to submit spam messages to spam@access.ironport.com or use one of our plugins (MS Outlook or Lotus Notes) to report these missed spam emails.
Best Regards,
Cisco IronPort Customer Support
