How 4 of the Top Mailbox Providers (ISP) Determine What Gets to the Inbox

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  • February 4, 2015

Today at the Email Evolution Conference put on by the EEC, a very informative panel consisting of Gmail, AOL, Outlook (Microsoft), and Comcast shed some light on a few questions that email marketers consistently ask us.

What affects deliverability to the inbox?

Many we already knew the answers to, but there were some nuggets of information that might have been unclear.  Below are some of the highlights we gleaned from attending.

On blacklists:

AOL uses SpamHaus CBL and XBL blacklists.  None of the other ISPs admitted to this openly, but Spencer Kollas from Experian Marketing Services believes most of them use it as a strong signal.  He mentioned in an unrelated session that they’ve seen 80-90% drops in engagement when listed on a SpamHaus blacklist.

Gmail stated they don’t really have a blacklists per se, as everything is determined via algorithms.  Many inputs (discussed below) are analyzed to decide an emails fate.

Microsoft’s solution is a hybrid of blacklist and algorithms.  Comcast is similar to Microsoft, but it was insinuated they’re not as advanced.

On engagement:

Gmail stated that signal from a user that something “is not spam” is an order of magnitude more powerful than the spam button.

Microsoft came out and stated that user engagement will NOT affect a senders overall reputation.  AOL and Gmail agreed with these statements.  Comcast, however, said that engagement does affect overall reputation.  For clarity, engagement WILL affect the ability to get to that individual user’s inbox.  Gmail stated that engagement will only affect reputation in a positive reinforcement only.

All of the ISPs stated they do not track clicks (mainly for privacy reasons, partially for technical reasons), but they do track opens.

There are a number of engagement metrics they track that do affect reputation and individual delivery, including some of the following:

  • OPENS are good
  • DELETE without OPEN is pretty bad
  • FILING an email is good
  • REPLYING to an email is very good
  • Adding to the ADDRESS BOOK is good
  • Moving from JUNK to INBOX is very good
  • Moving from INBOX to JUNK is obviously bad
  • The SPAM button is also obviously pretty bad

Gmail also stated that there’s a higher probability that someone will click the spam button if your email is in the “inbox tab”, and less likely if it’s in the “promotions tab”.  The message was:  don’t fight the tabs, they’re a good thing.

On domain vs. IP-based reputation:

AOL and Gmail stated they have been tracking both domain and IP-based reputation scores for many, many years.

AOL will actually do domain-based white-listing, but you better have your security policies (SPF, DKIM, and DMARC) locked down or don’t bother.  If you switch IPs, you’ll get stomped by their algorithms if you don’t manage your authentication policies well.  If you do manage them well, they will transfer your reputation over.  AOL also pointed out that you should be doing authentication for your active domains that don’t send email, so they don’t get spoofed.

Gmail added to this, stating that it’s still important to warm up any new IPs.  The system will quickly learn that you’re the same sender, but stated that your ramp up should be staged:  send ones… tens… hundreds… thousands… etc.  And don’t change your new authentication policies during the ramp-up.

Microsoft added that the biggest value to domain-based reputation for them is for IP moves.  If you’re doing a migration, they said to call and give them a heads up.  They also stated that the URL host domains (where you’re sending people to) holds more weight than the sending domain.

All of them stated, repeatedly, that setting up your authentication policies are vital.  It’s always surprising to us how many folks have issues with even just SPF.  We see a huge percentage of new customers with problems during onboarding.  Get these in order, people!

Oh…and subject line or body keywords are much, much less relevant than you think.  But, of course, crappy keywords might cause a user to not want to open!

On spam traps:

AOL will suspend email accounts after a time of inactivity, and they have occasionally turned those into spam traps in the past.  They didn’t say whether or not this is still a current practice.

Gmail said they don’t recycle or reuse accounts for anything.

Microsoft will disable an account if they haven’t seen a login in 2 years.  They do not reuse them for spam traps.

Comcast does not reuse them for spam traps either.  Their traps are typically random characters and obvious to spot.

Finishing up:

I will say this seems to have been one of the more open conversations we’ve heard from the ISPs directly.  We think this might have something to do with the fact that their algorithms are getting really good and they can afford to share more than in the past.

They have to filter out 95% of the junk that hits their front doors, and over the years they’ve gotten good at spotting the 5% of valuable emails that need to be delivered.  On top of this, they want a good user experience so people don’t declare “email bankruptcy” and head to another mailbox provider.  So, they will err on the side of caution to preserve inbox integrity.

The bottom line?  Getting to the inbox is still complex, and will likely remain so for a while.  The rules of the game are just changing and morphing, and doing so at a rapid pace.

EDIT:  Our friends at MailUp posted an article about the same session, with a different take.  Check it out for more info!