Diagnosing Delivery Problems


Diagnosing delivery issues can seem a bit overwhelming at first, but in many cases, a few quick checks in the delivery logs can give you a tremendous amount of insight into the current problems and potential fixes. 

First off, it's important to understand that most delivery problems are generally unique to a specific receiving domain. More importantly, bounces codes do not always mean exactly what they are meant to explain. For instance, MSN properties will almost always block an IP while returning a content block diagnostic code even when list related issues are potentially the cause. Ultimately, the best information comes from the friendly description on the actual bounce DSN (Delivery Status Notification). These can be found in the SMTP report explained below in Step 2. Even then, some responses are deliberately misleading. If you're confused, send us an email or give us a call and we'll be happy to explain things in detail. 

It's also worth mentioning that the ReachMail IPs are the first line of defense for the ReachMail customer. An IP or ReachMail mailing/tracking domain is more likely to be listed that the sender's domain. This is one of the major benefits of using and ESP like ReachMail. We protect your domains from being blacklisted or blocked by being this first line of defense or rather, the first domains seen in the message. Few systems, if any, will dig further than the first layer. 

Diagnosing the problem

Step 1 - Run the Reports tab -> Campaign Reports -> Compare Campaigns report and select several mailings from the last few weeks/days. The goal is to get a bigger picture perspective of recent delivery. Your domain builds a sending history with every message you send. That means that you can't look at one message as an isolated issue. Poor list stats from a message sent weeks prior can and will negatively impact the mail you send today.

Ultimately the first step involves making sure you are not breaching basic industry thresholds. Here they are:

  • Hard Bounces (invalid emails) - should be fewer than 1% of your total sent count
  • Spam Complaints (FBLs) - should be fewer than 0.1% (1 per 1000) of your total delivered count. **note we run this off of delivered. Since FBLs are complaints from those who saw the email and reported the mail as abusive, we should exclude the bouncing addresses from this calculation. The total sent count includes undelivered mail, and thus may skew FBL calculations if used. 

If your account is in violation of either of these two delivery metrics, address these problems now before moving on. Options include culling your list of all but the most recent year of opt ins or getting your list(s) cleaned through a data hygiene service like our partner Fresh Address. Sometimes both are necessary. The rate of invalid addresses from recipients opting in more than 2 years ago jumps exponentially in most cases. Starting by removing anyone added to your list more than 2 years ago can save you a lot of time and money if it comes to paying for a list cleaning. 

Step 2 - If your delivery stats appear to be within basic industry standards for HBs and FBLs then it's time to move on to a more detailed investigation. From a comparison report, focus on your open rates. Do they appear to be trending up or down over time? Do you see any big spikes/drops in opens? If you do, investigate the individual report in more detail to dig further. You should be targeting a 20% open rate at least. 

Go to one of the reports from a recent campaign, preferably one with a decent amount of soft bounces. Soft bounces, which are valid addresses being rejected, will often contain information relating to the reason for the block/bounce. Mail Block soft bounces are usually the most useful. General Bounces usually lack meaningful information. Export the bounces to a CSV so you can review those. 

Go to Reports Tab -> Campaign Reports -> SMTP. The SMTP log reports will give you the exact answers returned from the delivery attempt. There should be a response for every address in your lists. Copy and Paste an email that soft bounced from your CSV file into the report and hit search. 

SMTP 250 OK - successful delivery
400 level bounces (like 421 DYN:T1 from AOL) are temporary rejections which often infer that ReachMail should continue to try to deliver your mail
500 level bounces denote permanent rejection. ReachMail should NOT try to send this message again. 

It's possible to receive several 400 level bounces before a message is ultimately accepted. A 500 level bounces is considered not delivered after the first attempt where the 500 level bounce code appears. 

Here an example diagnostic responses on a bounce from AOL for a higher level permanent block:

smtp;554 5.7.1 : (RLY:BL) http://postmaster.info.aol.com/errors/554rlybl.html

Step 3a - You've identified the problem. Now what?

  1. Hard Bounces - Consider culling your list by sign up date. Most invalid addresses started off as valid ones on older lists. 30% of all email addresses change from year to year, so if you haven't sent to your list in a while, there's likely some invalid addresses in there now. The industry gives you a 1% leeway which is plenty of wiggle room for any sender that's actively monitoring their lists. For brand new senders with older lists or anyone trying to use a list that hasn't been mailed to in the last 3 months, it would be wise to take a second look before sending. List Cleanings through our partner Fresh Address can be very helpful when needed, but they do tend to deactivate a lot of addresses. We think they should be used as a last resort for anyone not able to filter their list data by sign up date or last purchase date where applicable.
  2. Spam Complaints (FBLs - Feed Back Loops) - A high complaint rate (above 0.1%) means your is not well received with your recipient base. This often stems from older lists where recipients have been receiving mail for more 2 years. To be sure, some recipients will continue to engage positively with your mail for many years. The key is to identify those, separate them from your entire list, and prioritize delivery to those that engage. 
  3. Soft Bounces. Soft bounces are valid addresses that are being rejected the receiving domain (e.g. aol.com). A good threshold to watch is 5%. If you're getting more than 5% soft bounces, something is wrong with the campaign that needs to be addressed. Don't wait to act either. Soft bounce issues that escalate to higher levels don't often fix themselves. Soft Bounces problems can be some of the most difficult to identify and address. They often go hand in hand with low open rates which we'll cover in the next part.
  4. Low Engagement (low opens) Open rates below 15%-20% should be viewed as problematic. Low opens, especially a pattern of low opens on several messages is a sign of a fatigued list. Perhaps the recipients have been oversaturated with mail. Perhaps they were interested 2 years ago, but aren't any more. The bottom line is that the receiving end is tracking this information. Are you? The more you mail to non-openers, the worse you look as a sender to the receiving end. Start by culling older signups from your list or using our engagement calculator feature to identify and set aside the non-responders for a period of time before mailing to them again. 

** Problems 3 & 4 are far and away the biggest issues facing all senders in today's email ecosystem. While there may not be a direct causal relationship between the two in every case, our stats show a high correlation between both metrics. Those that often deal with high soft bounce rates often have low open rates due to old, now-disengaged recipient lists. Culling the dead-weight from your sending lists can have an immediate positive impact on your delivery and will put you back on track to better inbox placement. 

Step 3b - Contact ReachMail support. Our experience in dealing with delivery can be put to use to investigate and ultimately help you recover from a downfall in your delivery. The earlier the problems are addressed, the better. 

In the case of the aforementioned bounce, it's likely that the sender will have seen the following bounce before it escalated to a permanent rejection. 

smtp;421 4.7.1 : (DYN:T1) http://postmaster.info.aol.com/errors/421dynt1.html

Addressing the problem early when the issue is still new can save tremendous amounts of time and effort. Waiting until a bounce has escalated into a more serious problem means it takes much longer to get the block removed, and a longer road for recovery of your delivery once unblocked. 

Consider setting alerts (Account tab -> Account Settings ->Alerts) in order to be notified when bounces get out of hand. Prompt action can mean the difference between a single bad day of bad delivery and weeks of headaches. 

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