AOL has set a very high standard for other ISPs in terms of both mail filtering and delivery support. They were the first ISP to provide clear diagnostic information in bounce messages, the first to provide senders with a feedback loop, and one of the first to offer whitelisting services.
Filtering decisions are based on a combination of sender reputation and email content. AOL users also have the ability to block mail from specific senders.
Gmail is a webmail service provided by Google. Gmail is one of the largest mailbox providers with millions of individual users. There are also a significant number of individuals and small businesses that host their entire domain at Google. Thus, Gmail's filtering scheme acts on domains that are not obviously connected to Gmail.
Hotmail
Delivering to Hotmail
Filtering decisions are based on a combination of sender reputation and email content.
Hotmail does limit the amount of mail a sender can send based on the reputation of the sender. Senders with a poor reputation may be limited to as few as 20,000 emails a day. Senders with good reputations sometimes see delivery problems, and may sometimes see Hotmail silently discard email they judge to be spam.
Yahoo has a complicated filtering setup that uses a variety of techniques to protect their users from unwanted email. They use a combination of rate-limiting and temp failing along with bulk foldering as defenses. Yahoo also uses some lists provided by Spamhaus including the PBL, SBL, and XBL.
Yahoo provides whitelisting and FBL services. For senders and ESPs to qualify for the Yahoo FBL they must sign their mail with Domain Keys or DKIM. ISPs are eligible for an IP based FBL. Whitelisting is available to senders who fill out an application and qualify.
Engagement Scoring is a way to tell which emails are the most effective.
Each email address starts at zero points and goes up and down depending on actions that occur.
Action Scoring List:
5 points for View
10 points for Click
Sender Score is computed by a third party.
For a list of tips on how to improve your sender score visit
We have a system for coloring IP addresses based on the sender score. Requires reputation monitoring to be turned on for those IP addresses.
Color Definitions:
Black means there is no reputation monitoring/sender score for that IP.
Green = High sender score which is good 75 or higher
Yellow = Neutral sender score with 40 to 74
Red = Poor anything under 40.
It helps give an idea which IP's are the best to mail from.
Today when sending an email campaign out the most important factor is your IP and domain reputation. In the old days, content filtering was the main method of filtering email into whether it was accepted and or if ends up in the bulk/junk/spam folder.
Now everything is based on user engagement. Meaning any action that the user does to an email message, whether it is opening the message, clicking links in the message, replying to the message, marking the email as spam, deleting the message, adding the contact to your address book, etc.
Tips for Warming up IPs and Domains.
Example sending for a 30 million account warm-up period. This is only valid if your data has little to no hard bounces. Any small amount of hard bounces can wreck ip reputation.
Day 1: 1000
Day 2: 2000
Day 3: 4000
Day 4: 7000
Day 5: 11000
Day 6: 18000
Day 7: 24000
Day 8: 40000
Day 9: 60000
Day 10: 90000
Day 11: 140000
Day 12: 180000
Day 13: 220000
Day 14: 300000
Day 15: 500000
Day 16: 650000
Day 17: 800000
Day 18: 1000000