Deliverability: 10 questions & answers


The deliverability of emails  is one of the most important criteria of an email campaign. Deliverability is the ability of an email to be routed from its sender to its recipient, all in a timely manner and in full. Deliverability therefore expresses the desire to establish contact with prospects.

A good deliverability thus guarantees that the emails have been received in inboxes, and are then able to be opened or clicked. It is therefore a real financial stake for your campaign: sending out emails that do not reach your recipient will be very costly and unnecessary, so no ROI. In addition, emails that do not reach an inbox make your campaign strategy ineffective and undermine your marketing efforts.

Mailpro focuses on deliverability. First of all, Mailpro offers you an efficient and fast routing that guarantees access to your inbox. However, you may lose in deliverability due to identification such as spam or mismanagement of your database. For this, Mailpro accompanies you with the email marketing blog and suggest that you consult this file on the 10 prejudices of advertisers concerning deliverability.

1. Deliverability is an extremely simple concept: FALSE

The deliverability measures through figures and email statistics the ability of a email campaigns to reach the prospects' inboxes. Deliverability is not a simple concept because several elements can have a negative effect on deliverability. In the same way that poor deliverability will negatively impact other aspects of your campaigns. Here are some examples:

Criteria that can negatively affect deliverability:

  • Be identified as spam (bad object, mail body)
  • That prospects report you as an undesirable
  • Send emails without using a professional solution like Mailpro
  • Use wrong forwarding addresses or bounces
  • Complaints from your prospects to organizations or to you

Poor deliverability will impact:

  • Your e-reputation
  • Your IP address will be blocked by ISPs
  • You will be temporarily or permanently blacklisted
  • Your entire campaign will be called into question

Deliverability is far from being a simple concept because it is at the center of an equation with multiple variables. You must therefore perpetually observe your deliverability using your email statistics.

2. Deliverability is just a matter of sending: FALSE

Deliverability is not just a matter of sending an email. Indeed, by sending emails in bulk, it is quite possible that you will get answers in return. Whether it's your prospects, organizations or even ISPs, you're going to have to answer them, or at least set up a response management system. If you do not respond to people who are complaining or ISPs requesting additional information, your e-reputation will fall and eventually your will be considered an advertiser with bad practices and will be blacklisted.

The answers will then be treated differently but mostly sent through specific email addresses, the title of which will be adapted to the nature of the answer.

  • postmaster@...: this type of address is very common and it's the least specific of all. It serves a bit of catch-all address, through which you can communicate with prospects about a complaint or question.
  • fbl@...: this is clearly the address that will allow you to handle complaints throughout the feedback loop.
  • abuse@...: this address allows you to manage the complaints through which you have been reported as spam.
  • alerts@...: allows you to retrieve the various alert elements such as actions identified as triggers for automation.

As you will receive emails, you will also need an email filter on your side. First, to store them according to inboxes, depending on the type of email you receive but also to avoid spam.

3. For my deliverability, the domain name does not matter: FALSE

You have a domain name for your website, and generally the hosts offer you "matching" email addresses to this domain name. Concerning your deliverability, we discern two cases: the first is when you send emails with an address having the same domain name, the second is when you outsource the sending of emails with your own domain name.

Let's take a closer look at the first case: so you decided to send an email campaign with an address that has the same domain name as your website. Imagine that sending from this address suffers from poor deliverability and you end up blacklisted or banned. Your domain name here is endangered, and therefore your website also. It is better to use subdomains to do email marketing. Similarly, you can opt for a sub domain by type of email so the bad deliverability of your promotional campaign will not tarnish your loyalty campaign.

Concerning the second case, this time you send an email campaign of one of your partners with your own domain name. Similarly, in case of poor deliverability, you put your own e-reputation into play for someone else. If you do this with multiple partners, you can choose different domain names (which may be subdomains of the same domain) with dedicated IP addresses. We will see later that shared IP addresses are not really recommended in this kind of cases.

4. Deliverability has nothing to do with IP addresses: FALSE

IP addresses and deliverability are closely related. Indeed, IP addresses are attached to the emails you send, they are therefore a parameter of your campaign and can impact your deliverability. In addition, an email campaign does not mean a single IP address.

Indeed, the estimated number of emails to send determines the number of IP addresses to be used. If you do not have enough IP addresses to route your emails you will be blocked, and on the contrary, ISPs find it particularly shady to allocate more IP addresses to a campaign than it's necessary. Similarly, for a certain volume of sent emails we prefer the dedicated IP addresses while for smaller volumes we can opt for IP pools.

IP pools

IP pools are shared IPs. With this system it's easy to determine the right volume of emails to send but also to make emails for several types of campaigns. However, as discussed earlier, the poor deliverability of one campaign may affect that of others. In addition, the sharing of IPs must be done equally between the different campaigns, otherwise ISPs will be intrigued to see flows of very different sizes.

Dedicated IP

Dedicated IPs are particularly effective when sending large volumes (> 10,000 emails per day). For very large email campaigns, one can then choose a pool of dedicated IPs, ie IPs coming from subdomains of the same domain. With dedicated IPs, you have an isolated flow for each campaign, so there are no interactions.

Buying IPs

You can also buy IPs, this allows you to keep your IP whatever happens even if you switch providers. Your work on your IP's e-reputation is retained regardless of your provider changes. However, purchasing IPs adds an additional cost to your email campaign.

Anyway, once you have your IP address(es), you must register them with WHOIS which is a directory of domain names. You will also include the different e-mail addresses mentioned above. This registration is important as it formalizes your domain name and allows you to be found, including being put in the ISP's white lists.

You can then perform several tests on your IPs before the release of your campaigns:

  • Reverse DNS: ensure that the IP matches your domain name and vice versa.
  • IP history: check the e-reputation of the chosen address and its history.
  • View the IP address on your site to give information easily to ISPs

5. Deliverability cannot be impacted by ID spoofing: FALSE

As an advertiser, you are not immune to identity theft. If this is the case, a spammer can very well use your domain name and your addresses and thus make you lose all the qualities of your deliverability. To avoid ID spoofing you must guard yourself with an authentication procedure. Several solutions are possible:

Authentication can really protect your deliverability from ID spoofing, so do not neglect it.

6. Bounces do not affect deliverability: FALSE

Bounces happen when you send an email to an address that does not exist or to a mailbox that is full. You will then receive an email that gives you the reason why your email has not been delivered. The management of bounces is therefore important for deliverability.

In the emails that returned you as a result of a bounce, a code gives you the type of bounce. Here is the correspondence between the code and the type of bounce:

  • The VERP: allows the detection and the automatic deletion of the addresses for which the emails are not distributable. Wikipedia gives the following example:
  • Envelope sender: wikipedians-owner + bob = @
  • Recipient: [email protected]

The bounce will be: wikipedians-owner + bob = @ with an empty envelope sender.

  • The hard bounce: this bounce indicates to the sender that the email address is not valid. The code is as follows: Diagnostic-Code: smtp; 550 No such user here
  • The soft bounce: a bounce that is sent when the recipient's inbox is full or temporarily inaccessible with the code: Diagnostic-Code: smtp; 552 Mailbox full

There are other categories of bounces, less frequent, but which are necessary to treat. The bounces are the best way to understand why your emails have not arrived at their destination, and thus modify your email lists in order to improve your deliverability.

7. The header of my email is not important: FALSE

The email headers are seen first by the anti-spam filters, so it is necessary to learn how to correctly build a header, which will guarantee you a good deliverability. Here's what to include:

  • An email address for complaints, the famous abuse@ or even a link to a complaint form (rarer).
  • A link to an unsubscribe page.
  • The data that identify you as a sender.
  • Note that you are doing mass emails by adding "Precedence: bulk".

8. There is no need to register on certain lists before starting to send: FALSE

Several white lists and registers exist and list trustworthy advertisers. You can therefore register (your IP, your domain names, etc.) on these lists to guarantee the deliverability of your campaigns:

  • ISP white lists
  • to register your abuse@ address
  • Acquire the various certifications that exist on the Web
  • which is the largest white list of advertisers

9. I do not need to watch over my deliverability: FALSE

First, you must observe your deliverability with your various tools, such as email statistics. On the other hand, deliverability can also be monitored with bounces, your e-reputation level or the effectiveness of your feedback loops.

Deliverability is a long-term struggle. Indeed, changes occur over time and it's a job on several fronts so you are obliged to dedicate a certain amount of time. Then, the deliverability is constantly changing, so you need to be ready at all times. Similarly, you have to watch over the white and black lists to find out where you stand.

Deliverability is also seen in relation to developments in anti-spam filters. To reach inboxes you need to be able to understand how filters are made and what ISPs expect of you.

Finally, monitoring deliverability is done by studying e-marketing techniques, which are constantly on a quest for optimizations.

10. Deliverability no longer has secrets: FALSE

To conclude, here is a final statement concerning vocabulary.

Bulk: Means "mass" in English and allows to identify your emails as such in the header. Moreover, the fact that an email is routed to the unwanted rather than to the inbox is called the bulking phenomenon.

Unsubscribe: It refers to unsubscribing to newsletters or emails from a brand or a company. Unsubscribing is a fundamental right for prospects, and in fact you must include a unsubscribe procedure (or at least a link to it) in ALL your emails.

E-reputation: Represents your digital reputation, your reputation online, all media combined. Subject to sudden changes, an e-reputation is very difficult to evaluate and maintain.

ISP: Internet Service Provider.

White List: List of advertisers that are recognized by ISPs as advertisers who have good practices, such as reliable advertisers.

Black list: List of advertisers who have not respected the email ethics and who are therefore banned from the mailboxes by the ISP.

Complaint: Can be made directly to the advertiser or to an organization. It comes from a prospect who expresses his or her dissatisfaction. A complaint must always be managed immediately in order to find a positive outcome.


Deliverability is a complex principle. It has a lot of consequences on your campaign, but also many of your campaign actions affect deliverability. Deliverability therefore has a reciprocal relationship with email campaigns. But remember, good deliverability is also a matter of adapting to new technologies, new trends, as well as new laws managing mass email.

However, you are not alone in this fight for maintaining and optimizing your deliverability. Mailpro helps you by providing efficient tools for creating email, database management and routing. Mailpro will monitor the results with your email statistics. Test our deliverability by opening a free account!

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