He gave me some tips that I could pass on to our readers. So here you go:

• Comcast really, really hates it when you send to an old list (with lots of undeliverable email addresses). If you’ve got too many emails on your list that no longer exist, Comcast will block your IP address. This is a very strong argument for cleaning old, inactive members from your lists. Yes, I know it feels safer to keep old members on the list, because the number of recipients looks so much bigger. Yes, I know your boss keeps telling you not to clean your list, because they don’t want to lose any prospects. But those bad addresses are just holding back your overall deliverability and keeping the good addresses on your list from getting your message. Yes, I have numbers to prove it. In a later post.
• Comcast doesn’t like it if you send too many emails all at once to them (this one’s kind of a no-brainer). Here’s what makes them different: they’ll actually TELL you how many you’re allowed to send at once.
• As you can see from this chart, the rate of emails you’re allowed to send to Comcast at once depends on your IP’s “reputation.”
• Your IP reputation is based on at least two factors: Authentication (a technology standard that’s used to prove an email is not a forgery), and the IP’s “Sender Score” (Your IP’s Sender Score is kind of like a credit rating, and it’s the folks at ReturnPath who issue the score). MailChimp customers – Authentication is free with every MailChimp account, and through our relationship with ReturnPath we monitor our senderscore closely.

For those of you familiar with ISPs and abuse desks in general, none of this is all that new. The interesting stuff is how forthcoming and helpful Comcast is with their error codes and rate limiting charts. Overall, their new Postmaster site is one of the best I’ve ever seen (look at all the handy RSS feeds):

http://postmaster.comcast.net/

If you’re new to all this, and wonder how this applies to you:

• Don’t send to old email addresses. You’ll get yourself (and other innocent senders) blocked.
• At some ISPs, old email addresses get turned into spam traps. You send an email to a spamtrap, and you are instantly blocked. We had a case of a MailChimp user who sent to a 10-yr old email list (totally opt-in, and the guy luckily had IP/timestamps on all subscribers) and one of the addresses had been turned into a spam trap. The impact on his deliverability from a spamtrap hit was instantaneous and dramatic. Keeping his proof of opt-in for so long saved his behind.
• If you’re sending your emails from an ESP (like MailChimp, Constant Contact, etc) that has shared IP ranges, then one bad apple can truly spoil the whole IP range. So it’s important to go with an ESP that closely monitors their deliverability, and punishes bad senders (it’s for the greater good). Quality over quantity.
• Don’t export your entire email address book and assume they all want to receive email newsletters from you. Address book dumps are full of old email addresses, and are one of the most common reasons I see senders get blocked. Other reasons include: Fish bowls, sharing lists, and buying lists.
• If you have an old list of people who opted-in to receive emails from you, but you haven’t sent them an email in a really long time (or ever), then you need to delete any emails older than 1yr, then send the remaining subscribers a “remember me?” welcome email. Here’s a good example.
• If you send emails on a regular basis, and you think your system is cleaning the list for you, you still might want to segment your list by actives vs. inactives.

Comcast isn’t the only ISP that hates it when you send to old/dead lists.  AOL’s postmaster talks about IP reputation and undeliverables here. ReturnPath, the experts on email deliverability, mentions undeliverables here and offers some tips. Laura Atkins from WordtotheWise talks about “Letting Go” of old members.

In general, there’s a shift (again) in the way ISPs and email receivers judge emails as spam or not. Instead of relying on blacklists or focusing on bad content, they’re looking at your overall reputation as a sender. And list cleanliness (undeliverables, hard bounces, spam complaints) are huge factors in determining how clean your list is.

Just recently, MailChimp has experienced some amazing growth, and so we’ve had to add more IP addresses to our delivery queue. That means we’ve had to re-submit all our IPs to all the ISP FBLs again.

Normally, each ISP has its own FBL, with its own set of requirements, application process, review process, and reporting format.

This time around, we’re noticing that nearly all the FBL application emails we’re getting back from these ISPs look exactly the same. Then we figured out why: they’ve switched to ReturnPath’s FBL service. This is nice, because: 1) we’ve been ReturnPath partners for a long time, and 2) hopefully, we’ll all have a centralized FBL system to work with (and submit IPs to), instead of managing so many different accounts with so many different ISPs.

They want to know if their deliverability will be any better if they use a dedicated IP.

It’s not a question we can answer with a simple “yes” or “no.”

Mark Brownlow has a good overview of all the different points to consider before sending from your own dedicated IP.

At MailChimp, whenever we setup a new IP address (either to add to our overall rotation, or a dedicated IP address for a high-volume customer) it takes time to “break it in.” Here’s what we go through…

The problem is, whenever you send lots of email from a fresh new dedicated IP address, ISPs will take notice.

Their filters will say,

“Hmm, that’s a whoooole lotta email coming from a fresh new IP we’ve never seen before. Must be an infected computer on a botnet, sending spam. I’m going to block those emails until they build up a good sending history.”

And they watch email volume from that IP.

It can take weeks or months for them to finally come to the conclusion:

“Okay, apparently it’s normal for this IP to be sending so many emails, and overall, we haven’t received too many complaints or spam reports, so let’s just consider this IP trustworthy.”

For example, here’s a MailChimp IP address as seen by Trusted Computing’s TrustedSource Internet Reputation Monitor:

This particular IP address has been in use for years, so they’re kind of used to receiving tons of emails from it. See how they watch “deviation in message count” over time?  There are normal “ups and downs” that occur (weekend traffic is generally down), but overall, things are pretty consistent. So our “Sender Reputation” is nice and green.

Now here’s what happens when we recently turned on a fresh new dedicated IP address for a customer who sends hundreds of thousands of emails, almost daily:

As you can see, email volume is non-existent until late July. Then, we turned on the IP and everything goes red, and we look like a “malicious sender.” But the truth is, there’s nothing “malicious” about the emails being sent from this IP. They’re actually extremely good (and opt-in of course). You’d laugh at all this “malicious” terminology if you saw the squeaky-clean emails this customer is sending. It’s just A LOT of email, happening all at once, from an IP that never sent any emails before.

To try to offset the high volume from this new IP, we take huge chunks of their campaign and dsitribute those across our shared IPs. Only a small fraction of this customer’s email is actually being sent from this dedicated IP during the break-in period. But as you can see, for some filters, it’s still risky looking. And so you get delivery problems for a while.

So long as the volume stays somewhat consistent, and so long as spam complaints stay within acceptable thresholds, their dedicated IP will make its way to “Trusted.” Actually, it’ll go to “neutral” for a while, then trusted.

But just because email volume looks suspicious, it doesn’t mean you’ll be totally blocked.

It’s more complicated than that.

Email Reputation Is Like Your Credit Score

MailChimp subscribes to ReturnPath’s Reputation Monitor. It gives us a birds-eye-view of how our IPs are doing. We like ReturnPath, because they also just so happen to manage the feedback loops for a LOT of the big ISPs out there.

Anyway, we don’t just send all emails from one IP. And we don’t just spread them out equally across a bazillion IPs. That would be stupid.

We have several different “ranges” of IP addresses. Some are “shared” (free trial accounts, & new customers), some are “trusted” (long-time users with good stats), some are “double-opt-in” (people who have never imported any outside list, and have only used our double-opt-in process), and a handful are “dedicated” (high-volume customers who purchased and setup a dedicated IP). The “deliverability” score for each range is different. As you would expect, the “double opt-in” range gets a slightly higher score than the “shared” range. They say the average score out there is 88%.

Now here’s how that same dedicated IP address I mentioned above looks to ReturnPath, compared to a few of our other IPs:

As you can see, the Accepted Rate  (which is basically the number of emails that weren’t rejected by the ISPs they monitor)  is actually higher than a couple of our other “shared” IPs. At least for today, it’s getting a 98.13%. Not bad. But you’ll notice that one of our shared IPs (mcsv15.net) has a higher “Sender Score” (95) than this dedicated IP (80).

How could that be? And what’s a Sender Score mean, anyway? We have no friggin’ clue.

Here’s ReturnPath’s definition of SenderScore:

This score is derived from a proprietary Return Path algorithm, and represents your overall performance against metrics important to both ISPs and recipients of email. Sender Scores are on a scale of 0 to 100, with 0 being the worst, and 100 being the best score. Like a percentile, your Sender Score tells you how you compare to other email senders. For example, a score of 70 indicates you are measured as better than 69 percent of all mailers, and worse than 30 percent of mailers.

As you can see, their algorithm is super secret, so we have no way of knowing exactly how our Sender Score is derived. But the number is pretty important, because more and more ISPs and spam filters are using ReturnPath’s scoring system:

Receivers use the top level scores, and (for receivers who contribute data) rules based on specific data elements as inputs to their mail filtering decisions. A simple implementation may be to reject all mail with a volume above some lower limit and a Sender Score beneath some level they deem acceptable. A more complicated implementation may be to whitelist IP addresses with Sender Scores above some threshold but blacklist senders who have recently hit a spamtrap, or who have generated very high complaint rates.

And here’s a list of some of the ISPs and spam filtering companies who use ReturnPath’s Sender Score Certified rankings. Long story short, the score is mysterious, but the score is important, because it’s used by ISPs to filter incoming mail.

So why does our dedicated IP address get a lower Sender Score? The answer could be in that “Problems” column: “Mailing Consistency.” Over time, the email volume from this IP will appear more consistent, and the score will go up (so long as the sender doesn’t goof up with a campaign, and generate a lot of spam complaints).

Getting a high volume of emails delivered is complicated. A colleague here at MailChimp describes it like “cell phone dead zones.” Sometimes, you get a dropped call. People have come to expect a certain level of reliability, but they aren’t shocked if they drop a call in the middle of a desert.

Email receivers are all constantly trying to find newer, smarter ways to filter out spam. A dedicated IP address is not a silver bullet. Today, at least. It’s true that a dedicated IP address will isolate you from any “bad apples” that might be on a shared pool of IPs. But if you’re using a decent email service provider, there shouldn’t be very many “bad apples” on that shared system anyway. Hopefully, they have some kind of review process that keeps bad apples from even joining (at MailChimp, our human review team scans about 30 different criteria to determine if a user is safe enough to send). And so you can piggy back on that shared IP range, because there’s “strength in numbers.” Then again, you may be a financial institution doing some intense authentication, and you absolutely positively need a dedicated IP. If you have the patience (and volume) to break one in, you might get better inbox acceptance rates. If you also have the budget to get the IP SenderScore Certified, you can get whitelisted by some ISPs and spam filters. But if your volume isn’t consistent, or if it’s sporadically high, your overall reputation score may suffer, which could result in delivery problems. Some people (especially those who are new to email marketing) are better off using a shared IP, while they build up their lists and hone their good email habits.

It’s a lot like your credit score. There are tons of factors that credit agencies look at to determine your score. And there are different credit agencies with different scoring algorithms. A person with a ton of money in the bank can have a terrible credit score, just because they don’t own a credit card, and never take out any loans, and always pays with cash. There’s simply no history to reference. And when that person is finally ready to get a credit card or loan, their low credit score will hurt them. Eventually, they’ll get a credit card, and build up a strong history. Maybe even get a great credit score. But if the person tries to buy too much stuff at once, it might trigger a block at the credit card company, resulting in a really awkward moment at the cash register.

ISPs and receivers do the same thing. They can’t peek into your office or look at your financial records to determine that, “Okay, this dude seems legit, so let’s whitelist him.” They have to look at your email reputation, which is composed of your email activity, like: volume consistency, abuse complaints, server setup, and content.

See, I told you this was going to be a complicated answer.

A: In your MailChimp campaign stats, you’ll see the number of people who complained about your email (by clicking on the “Report Spam” button in their email program). That number comes from MailChimp’s integration with major ISP feedback loops, like Yahoo, AOL, Microsoft Hotmail/MSN, Outblaze, Roadrunner, Comcast, and more. It’s not uncommon for subscribers who requested email from you to still report you for spamming.

There are a few reasons this could be happening…

1. They forgot you.
Did you wait too long in between collecting emails and sending your campaign? If so, some of your recipients may have just forgotten who you are.

2. They didn’t recognize you.
Was the from-name in your  email campaign instantly recognizable? Did you use the company name that they saw when they subscribed on your website? You didn’t change branding, did you? If your company name is “Acme Food Services”did you use “AFS” and assume they’d recognize that in their inbox? Was your company logo visible in the preview pane of their email program (see our Inbox Inspection tool)?

3.  Did you set proper expectations?
When people signed up for your list, were they expecting something different than what you sent them? Were they expecting a different frequency, perhaps?

4. Was the list truly “opt-in”?
Some people say, “but my list is opt-in” but what they mean is, “but I bought this list from a source who claims this list is opt-in.” If they didn’t request emails specifically from you, that’s not what we mean by “opt-in” and you totally deserve those spam complaints.

Apparently, some marketing folks (Q Interactive and MarketingSherpa) ran a survey that suggests the button is meaningless now. That’s because too many people click “Report Spam” when all they really want to do is unsubscribe.

This statement from Laura Atkins is what I found most interesting (which I’ve summarized in a very unprofessional way below):

“I think this is a demonstration of the disconnect between traditional marketing (telemarketing and direct mail especially) and email marketing. In traditional marketing…recipients do not have an easy way to send negative feedback…In email marketing, however…they have a way to communicate back to the marketer that they do not have in other forms of marketing.”

There’s definitely a “disconnect.” Enlightened marketers know how to treat email. Ignorant markters who just treat email as “cheap direct marketing” are ruining email for all of us, and need to have their computers taken away from them.

As co-founder and abuse desk admin at MailChimp, I see this disconnect all the time from old school traditional marketers. Whenever I have to investigate a user’s account for too many spam complaints (generally, more than 1 per thousand recipients) or way too many bounces, I hover my finger over to the “SHUT ACCOUNT DOWN” button whenever I hear the following “traditional marketing” excuses:

• Dude, I get tons of junk mail in my mailbox every day. What’s the difference with emai (click)
• Oh c’mon, everybody knows when they drop their business card into a fishbowl they’re gonna get (click)
• Perfectly legit list, man. We got it from the local Chamber of Comm— (click)
• But I bought that list from a really expensi— (click click click click)

All of the above are great ways to send traditional, offline marketing. But not mass email. Ignorant marketers just don’t get that. But this is a no-brainer for marketers who actually have a clue about email.

Remove Tin Foil Hat. Step Away From The Computer.

Even the best email marketers get 1 or 2 abuse complaints (and that’s why ISPs have pretty reasonable thresholds). But good marketers look at those complaints as “feedback” (by the way, ISPs use the term “Feedback Loops” when they refer to those report spam buttons).

They don’t think it’s some kind of conspiracy to get their companies blacklisted, and they don’t think the ISPs and spamcops are “out to get them.” Trust me, they probably don’t even know you exist. If one of your campaigns suddenly gets a lot of complaints, this is great user feedback that something’s wrong with your marketing. Don’t you wish you could get that kind of instant feedback from traditional direct marketing?

If you’re getting too many feedback loop complaints, don’t cry about it and demand that ISPs change their ways. Take a long hard look at your email marketing opt-in process. You’re probably sending too much email, or unexpected email, or you’re not managing your lists properly,  or some combination of the above.

Related:

Obsessed with Open Rates? Stop it; Focus on Feedback Loops