Email Marketing: the problem of deliverability

spam email deliverabilityDeliverability is the main critical factor of any email marketing campaign. With the term "deliverability", in fact, means the ability of a campaign perpetrated by electronic mail to reach efftivamente the mailboxes of the recipients.

One of the most common mistakes when you approach for the first time to the market of email marketing, in fact, is to consider certain delivery of every email sent: 1,000 emails sent, in fact, almost never match in 1000 succeeded contact details in the boxes recipients' mail!
But why is this happening? Why an e-mail sent properly can not reach their "target"? In the remainder of this article we will try to understand the reason for the lack of contact, and what remedies you can take to improve the performance of our mailings.

But because the mail does not arrive at their destination?

The problems that can result in non-delivery of mail are manifold. First, without a doubt, the most critical factor can be identified in the work (not always perfect) of the anti-spam filters.

The anti-spam filters and the problem of false-positive

Spam (junk mail), as we know, is one of the major scourges of the Network and to combat the main provider of mail services over the years have adopted various countermeasures that, at least in part, have failed to stem the flow at the expense, unfortunately, some "innocent victim".
Inferequente is not, in fact, a perfectly legitimate mail (sent, that is, with the express permission of the recipient) is automatically "branded" as spam and end up in the junk folder: one described is the phenomenon of so-called false positives, ie legitimate emails that are erronemaente classified as unwanted.
The fate of these emails, unfortunately, never to be read at the expense of the sender (which, although well-intentioned, has seen stuck his message) and the recipient (which probably has not received a statement of interest) .

Mailbox closed, locked or full

It may happen that a user of registering a service by leaving the email address of a box that shortly after, could be closed or no longer used.
In these cases, as is obvious, the mail does not arrive at its destination but will generate a bounce that is "a step backwards with the message" (as undeliverable), accompanied by a brief description of the problems that have prevented delivery.
The management of bounces, as we shall see, is one of the most important tasks in the management of non-extemporaneous email marketing.

Issues Network

Sometimes it may happen that a mail is not delivered due to problems of network that prevent the proper routing of the message: it can happen, for example, that the target server is down or overloaded, or that the network is blocked as a result of malfunction.
In these cases, usually the email is delivered with delay (the mailserver make several attempts in case of problems of this kind) but it is not inconceivable that, even inability is prolonged and the item does not complete.

Why are my emails are classified as spam?

Let a necessary clarification: In this article we are talking about emails sent legally but unjustly detained. The phenomenon under study, therefore, is that of "false positives" and not sure you want to explain how to evade anti-spam systems to send junk mail to unsuspecting recipients.
With that in mind let's start by saying that the reasons for such an eventuality (not Coretta classified as spam) are more than one, analiziamoli:

The content of the message is suspicious

This is the most common type of control and is based on the actual content of the message sent.
To give an example, think of the messages written in Chinese, Russian or Italian ungrammatical: anti-spam software (such as Spam Assassin) are able to recognize these abnormalities and to block them. But not only just blunders the cause of missed deliveries, also the frequent use of words like free, free, download, etc.. shall be considered suspect.
Equally suspect is considered to be a message in which the images are excessive compared to textual content, or the HTML format of the email is malformattato or contains such elements.
If the cause of your block resides in the body of the message, well ... your problem is easy to solve: just restructure the content of your email in order to increase the rate of deliverability of your campaigns.

The mail server is an Open Relay

Another problem is the relatively common misconfiguration of the mail server delegated to the actual dispatch of email. A misconfigured SMTP, in fact, could be blocked by the target systems with a consequent fall in the rate of deliverability of your messages.
The most serious risk to a mail server is to be classified as Open Relay, ie, a system can be easily used by anyone as a "cannon" fire email!
More technically, a mail server is identified as Open Relay if instructions to be sent by anyone regardless of whether the applicant has the necessary permissions to access the service.
If your mail server is misconfigured and the definition of an Open Relay, then it is highly likely that the non-delivery of your mail is due to the absolute unreliability of your paging system which, precisely because it unreliable, it is blocked by the target server who reject messages.
To verify the proper configuration of your system, you can use the system made available by or use the automatic verification tools provided by CheckOR.

Improper DNS configuration and / or non-use of authentication systems


The first thing to do as it prepares a separate shipping system is to make sure that the DNS are set correctly. The configurations most important from this point of view are:
1) setup PTR (for reverse DNS)
The PTR record, in fact, performs the inverse operation to that of the record: if the latter with a hostname is associated with an IP address, with an IP PTR record is reconnected unequivocally to a hostname.
This is, to date, very important because most of the mail server when they receive a message from a given IP verified (by, in fact, a reverse DNS lookup) that is connected to that IP address to the hostname of the sender.
In practice:
A server receives an email message from the IP address that says his name
At this point the server A performs a reverse DNS on the IP to verify that actually corresponds to
If successful, the email is delivered (or rather, the other goes to a control phase) otherwise it is marked as spam
2) configuration of SPF records
The SPF record is a particular configuration of DNS that allows the mail server of the recipient to verify the true identity of the sender.
SPF stands for Sender Policy Framework and is a very simple system that allows you to check if the server has sent a message is authorized to do so for the specific sender.
Basically, adding an SPF record in the DNS, we can elect our server as "agents" of trust (and therefore reliable). Let's take a practical example that is related to the previous one:
Suppose that the server send an e-mail from the sender
The destination server (after the checks above) will check if you have set an SPF record for the domain ""
If the DNS domain is NOT an SPF record the mail may be classified as suspected
However, if there is an SPF record that says is considered a legitimate server the mail will pass the test, otherwise (the server that sent is not listed as authorized) will be blocked
To signal the existence of a variant of the SPF record, known as SenderID (a system promoted by Microsoft, but that, in fact, has had little below) which effectively performs the same operations described for SPF.
3) Configuring DomainKeys and DKIM
DomainKeys and DKIM (DomainKeys Identified Mail) are two authentication systems of e-mail messages that allow recipients of a message to ascertain its true source. The main purpose of these technologies is to combat the Phishing avoiding, ie, that are delivered mail that simulate a sender different from the real one.
To simplify the operation of these two technologies is based on a public key (published in the DNS domain) and a private key that is used to "sign" all outgoing e-mail messages. In this way, the customer may, by asking the sender's DNS, verify that the signature in the message is compatible with the Chieve public.
If successful, the message will be classified as safe and will be delivered to the recipient's Inbox, otherwise you will be thrown into the trash can of spam.
To use DomainKeys and DKIM is necessary to intervene on DNS and use on your mail server with the appropriate libraries are able to add headers (headers) to outgoing email. This type of operation, therefore, requires skills rather high and must be performed by the system administrator of the mail server.
4) implement DMARC
Following an agreement between the major players in the network, was introduced a powerful new control system that takes the name of DMARC (which stands for Domain-based Message Authentication, Reporting and Conformance), which looks like a complete SPF and DKIM (which constitute the requirements).
Through this system, in the future it will be possible to drastically reduce the problem of Phishing safeguarding the safety of users and the proper functioning of the network as a whole.
Through DMARC, in fact, a sender can publicly state the rules for mail from your own domain when it is not relevant to the allegations with SPF or DKIM does not exceed the control: through a specific string entered in the DNS, in fact, the holder of a domain can instruct the mail services from around the world about the behavior to be held against email validated with SPF and DKIM (you can ask, for example, of resisting them!).
But not enough, through DMARC you will receive (via email through the address listed in DNS records) of the daily reports about the flow of mail received incompatible with SPF and DKIM.
The use of this technology, which will be essential for banks and online services of various kinds, it will certainly be very useful also for the reputation of anyone who uses email as a means of continuously mass communication.

The sender's IP is blacklisted

One cause of non-delivery of messages is, certainly, being present within one or more blacklists.
The entered IP blacklist, in fact, are not accepted as valid senders and their messages are rejected or relegated to the junk folder.
Unfortunately end up in a blacklist is something much more likely than you might think and it can happen even if you take the ethical behavior (due to, for example, unfair complaints from some users of our list).
It 'a good idea, therefore, to constantly monitor the presence of our mail servers within the most widely used blacklist. To do this we can use various online services such as, for example, that offered by MXToolbox.

The IP address of the sender has a low reputation

Even if you are not present in any blacklist, it can also happen that the IP of our mail server "is not well seen" by the anti-spam systems set at the head of the boxes of our recipients.
This can happen because, although not banned, our IP has a low reputation! But what is the reputation of an IP?
The reputation of an IP is its reliability according to some metrics that take into account several factors such as:
  • the old IP address (an IP recently will be considered less reliable than an old IP)
  • the volume of the sending (an IP that sends consistently be considered more reliable than one characterized by ups and downs in the flow of shipping)
  • amount of bounces (the number of contact failures as a percentage on the total items have a profound effect on the reputation of an IP address)
  • amount of spam trap in which he has fallen (an IP that has fallen in various spam traps will certainly not be trusted ...)
If you want to measure the reputation of the IP votro I recommend you use the services offered by sites SenderBase is Senderscore.

How to improve deliverability

After analyzing the various aspects that can affect the deliverability of an email marketing campaign, we now review the possible solutions to overcome (or at least mitigate) this issue.
Properly configured your mail server (and make sure it is not an Open Relay)
Work on the authentication of mail and implemented:
  • The PTR record for Reverse DNS Lookup
  • The SPF record
  • The authentication systems DomainKeys and, especially, DKIM
  • Evaluate the possibility to join the system DMARC
Make sure that the IP address of your mail server is not present in any blacklist, if so immediately Strive to ask for the removal (by completing the appropriate forms provided by the various associations that manage RBL and DNSBL)
Work on the reputation of your IP being sure to maintain a high level of public accountability of your mail server: not "match in the fifth" But grow slowly in the number of items taken and cancellation policies easy and transparent (of course, avoid like the plague to send email unsolicited!)
If possible try to get a place in any Whitelist: between the services of this kind the best known and most important is certainly the one offered by Return Path offers a real certification for e-mail senders to ensure their (through agreements with leading players in the market for email) really high deliverability rates, the only problem with systems like this is given by the cost (not for everyone) and its high level of quality required for certification
Manage carefully the quality of the list:
  • Use rigid registration policies able to monitor the quality of requests for inclusion in the list (always use the Double Opt-In)
  • Adopted cancellation policies clear, easy and transparent by including in each message sent the link to request exclusion from the list
  • Always remember your users the reason for which they receive your messages and included in every email a brief policiy about privacy management
  • Managed in a timely manner to avoid any bounces to continue to send mail to addresses that are not accessible
  • Subscribe to the various programs FBL (Feedback Loop) to receive communications from the provider about any spam complaints received from users who receive your messages
Set up carefully the content of your email:
  • Make sure your software correctly handles the headers of messages
  • If you send HTML messages make sure that the code is valid (using proper validation tools like the one offered by the w3c)
  • Make sure there is balance between the text content and markup (HTML code and too little content poses a serious risk of ending up in spam)
  • Do not create posts consist of images only (try to maintain a euqilibrio between images and text content)
  • Avoid putting hidden elements in the HTML
  • Avoid using frequently words like free, free, etc..
  • Make a spam-test your message before proceeding with the shipment; many programs to send mailing lists contemplate this feature, otherwise you can use the online tool like this



Manage the 'home' mailing list is becoming increasingly difficult, and if a few years ago it was possible to manage internally and with good results lists also large, today the use of systems and skills has really become inevitable.
Adopt "do it yourself", in fact, inevitably leads to a deterioration of the list and its chronic inability to reach the target in an effective way, which - sopèrattutto for those in the business of sending for professional purposes - can cause damage to very high levels of : have a list of 10,000 addresses of potential customers and can only reaching 1000 means giving up to 9,000 potential buyers for our products and services!
For this reason work on deliverability is increasingly important in order to be able to obtain the best possible result from our valuable database of contacts.
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