We are receiving several support tickets from users complaining about Yahoo! users being unable to send them emails. Please be aware that Yahoo! currently has several of their IPs listed in SpamCop, a Real-time Black Hole listing service.
Users are reporting bounce back messages that say something like:
"Remote host said: 550 http://www.spamcop.net/bl.shtml?18.104.22.168"
Please understand there is nothing we can do about this. This is an issue between Yahoo! and SpamCop. Apparently from what we have been able to find, Yahoo! has their services get exploited to send out spam messages and they hit a spam trap email address (a spam trap address is an email address that exists only for the purpose of collecting spam. Any mail that is received at a designated spam trap address is unsolicited).
Cisco Systems purchased IronPort a few years ago. IronPort runs the Senderbase reputation system and SpamCop Real-time Black Hole listing service.
According to Senderbase, Yahoo has 5,507 email servers. There are a few servers at Yahoo that are on a block list (or RBL) at any given time. Most people never have this problem receiving email from Yahoo!, but others have it happen frequently. It is a random chance that the email will go out a server that is listed on SpamCop.
I would encourage any Yahoo! user that is affected by this to voice their concerns with Yahoo! Finding a contact link for Yahoo! is difficult, so it would seem that twitter might be the best way to contact them concerning this. You can find Yahoo’s twitter account at @YahooCare.
Nobody likes to receive spam and it would appear that Yahoo!’s policies make it far too easy for spammers to use their network to send out unsolicited messages.
This is a response from an Admin at SpamCop.
This IP address is a webmail server that belongs to Yahoo! and is being used to send out large amounts of spam, including fake pharmacy spam, fraudulent 419 scams and others. The amount of spam being sent through Yahoo! has grown exponentially to the point it is tripping our listing defenses.
We can do nothing to stop the spam at its source, but we can help others block spam, including those that have chosen to refuse any mail from identified spam source IP addresses. Only Yahoo! can stop the spam coming from their network. You should contact Yahoo! with your complaints as only they can stop the spam. Once the spam is stopped, or at least slowed, the server IP will delist from the SpamCop Blocking List.