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2016

In a previous post, I talked about troubleshooting hard bounces.  In this one, I'm going to talk a bit about soft bounces, specifically soft bounces due to throttling.

 

What is throttling?

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Throttling is an issue that occurs primarily with the large Email Service Providers (ESPs) such as AOL, Yahoo, and Hotmail.  When the ESPs are experiencing high volumes, they will throttle bulk email senders such as Marketo.  It works kind of like this:

 

Marketo walks up to ESP with a big basket of emails.

 

Marketo: Hi, I'm here to deliver these emails--

 

ESP: I'm busy.  Come back later.

 

(Two minutes later)

 

Marketo: Hi, I'm back to deliver these emails?

 

ESP: I'm busy...Fine!  I'll take this many. (Grabs a handful of email.)

 

Marketo: What about the rest?

 

ESP: Come back later.

 

(Four minutes later)

 

Marketo: Hi, I'm back to deliver these emails?

 

ESP: I'll take this many. (Grabs a handful of email.) Come back later.

 

(Eight minutes later)

 

...The cycle repeats with the time interval doubling each time.

 

 

Marketo is pretty patient, it will keep coming back and trying to deliver for 24 hours (36 hours for AOL). While it is still attempting to get the ESP to accept delivery on the emails, the emails will show in reporting as status "Pending."  Once the 36 hours are up, Marketo will give up and bounce or soft bounce the emails as appropriate.

 

The challenge with throttling is that it's like weather or traffic congestion - there's not a lot you can do about it.  One strategy is to break out your sends into smaller blocks - if you think of Marketo with the basket of email, it might be better to have multiple baskets and hope that the ESP takes a handful from each one.  If you have a large number of leads on the commercial ESPs, you might even want to break each one out to a separate send.  This doesn't necessarily help with the throttling, but it does give you better visibility to possible throttling issues that may be occurring on a specific ESP.

 

A third strategy is to try and massage your sender reputation, to make the ESP more likely to accept your email.  To go back to my nightclub analogy, if you have a bunch of girls who want to get into the nightclub together, they usually send the cutest one of the group to go charm the doorman.  From an email perspective, you want to send to your most engaged leads first - people who are likely to open and click on your emails, improving your reputation.  The next day, you send your somewhat engaged leads, and the day after that, your least engaged leads.

 

If you are in the B2B space and don't deal much with the large consumer ESPs, the chances are that throttling won't have a big impact on your deliverability.  In the B2C space, however, throttling can definitely step on your overall email performance.  Setting up reporting to keep an eye on your emails and trying different strategies to mitigate the effect can be an important part of your email marketing practice.


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Let's say that you have a weekly newsletter that you send out through Marketo and every week your deliverability is 95% or better - except last week!  Your deliverability was only 80%!  What the heck happened!?

 

To find out, we pull up a quick Email Performance Report for the email in question and see what it says.  Let's say, for the purposes of this entry that you see a big spike in hard bounces.  (Soft bounces deserve their own write-up.)  I should clarify what Marketo considers a Hard Bounce.  Marketo considers a bounce to be a hard bounce if we get a definitive "NO" from the recipient server.  The server might say "NO" to the delivery because the email address is invalid, or it could say "NO" because it believes the email is spam.  How do we tell whether our spike in bounces was due to invalid emails or due to spam rejection?  We can do this with a Smart List, using the filter 'Email Bounced' and the 'Category' constraint.  Category 1 bounces are spam bounces, Category 2 bounces are invalid email addresses.

 

If the majority of the bounces are Category 2 - Email Invalid, then you will want to go back to your lead database to see if new leads were added, perhaps incorrectly.  However, if the majority of the bounces are Category 1, we need to figure out how you got flagged as spam.

 

When an email to a lead bounces as spam, a couple things happen.  The first is that the lead is set to Email Suspended, and the suspension lasts 24 hours.  During that time, it cannot receive any emails from Marketo, and it is not possible to undo the Email Suspended.  You just have to wait it out.  The field 'Email Suspended' is a historical field.  A more accurate name for this field would probably be "This email was suspended at some point in its history."  The actual suspension only lasts 24 hours, so to see if the lead is currently suspended, check the timestamp on the 'Email Suspended' field.  If it is more than 24 hours ago, the lead is not currently suspended.

 

The second thing that happens is that the actual bounce message received from the recipient server is written to the 'Email Suspended Cause' field.  This field can be full of great information.  To make use of it, let's go back to our Smart List of Email Bounced, Category 2 leads and edit the view so we can see the 'Email Suspended Cause' field.  You will probably need to extend the width of the field to be able to read the bounce messages, but once you've done so, you will be able to scroll down the list of leads and read all the bounce messages we received.

 

A note about bounce messages: they aren't standardized so don't get too wrapped up trying to decode them.  The admin of an email server can configure their bounce messages to say literally anything.  I saw one bounce message that simply read "Go away."  Some will be totally generic, some will be strings of meaningless characters, but some of them - the ones we are looking for - will tell us the name of the blacklist that caused the email to be bounced for spam.  The most common is Spamcop and the bounce messages may look something like this:

 

550-"JunkMail rejected - em-sj-00.mktomail.com [199.15.214.200]:48340 is in an 550 RBL, see Blocked - see http://www.spamcop.net/bl.shtml?199.15.214.200"

 

You may also see blacklists for Symantec, TrendMicro, or ATT.Net.  While they are independent and maintain their own reasons for listing, they often reference major blacklists such as Spamcop and so a Spamcop hit can have far reaching consequences.  Marketo actively manages our relationships with the various blacklist organizations, and some delist automatically after a certain period of time, so by the time you get around to looking at your deliverability for an email, we may be back off the blacklist.

 

Seeing Spamcop in your 'Email Suspended Cause' field, your next question is likely to be "Did I hit a spam trap?"  The answer to that is a maybe, but maybe not.  If you are on a shared IP, it may be that someone else on the IP hit the spam trap, but everyone using that IP is affected.  I think of being on the shared IP sort of like being a tenant in an apartment building.  If one of your neighbors accidentally starts a fire in their living room, you get evacuated from the building along with everyone else, even though you never so much as struck a match.  It's one of the downsides of sharing a resource with other people.

 

If it was you that hit the spam trap, Marketo will notify you and request that you go through the remediation process to remove possible spam trap leads from your database.  If you fail to do so, you will be moved to the quarantine IP so that you can't continue to impinge on the deliverability of your neighbors.

 

Chances are, however, it wasn't you.  The short-term solution is to wait out the 24 hours and resend the email to the people who didn't get it.  But what's the long-term solution for people who don't hit spam traps and who don't want to suffer because of someone else's poor sending practices?  There are two options.  If you send at least 100k emails per month, you can get a dedicated IP - move out of that apartment building into your own home, so you aren't sharing a roof and walls with anyone else.  If you send less than 75k emails per month and you haven't hit any spam traps yourself, you can apply for the Trusted IP range, which is a range of IPs reserved for Marketo accounts whose clean email practices keep them out of spam traps and blacklists.  If you would like to apply for the Trusted IP range, you can do so here:  http://na-sjg.marketo.com/lp/marketoprivacydemo/Trusted-IP-Sending-Range-Program.html

 

If you don't see any indicators of blacklists in the "Email Suspended Cause" field (which is what it will be, 90% of the time), and instead you find a lot of generic bounce messages - "Blocked by policy", "Access denied" - then make sure your DKIM and SPF records still verify.  I've seen more than one SPF or DKIM record removed by IT staff who didn't realize it's importance, and more than one email sent using a domain in the From: line that wasn't set up with SPF and DKIM.


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