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The Great Email Deliverability Guide

In view of the large number of competitors and massive amounts of spam e-mails being sent, secure delivery of electronic mail is more important than ever before.

And that doesn't just apply to marketing emails: Just think of your last concert tickets, flight tickets or order confirmations. These transactional e-mails also have to find their way safely and reliably to your mailbox.

The deliverability of e-mails is of fundamental importance. For this reason, read in this article what you can do to ensure that your e-mails land in the inbox and which stumbling blocks you should avoid.

E-mail reputation: Your deliverability depends on this

Your reputation as a sender of email marketing campaigns is comparable to a digital certificate of good conduct.

It plays the main role in the question of a good delivery rate.

If you send campaigns with valuable content to recipients who have signed up for your contact list and follow the current best practice in the field of e-mailing, you will be rewarded with a positive reputation.

This increases your chances of being viewed by the respective Internet service providers of your recipients as a trustworthy sender and of ending up in the mailbox.

However, if you send unsolicited bulk e-mails to e.g. purchased contact lists, your campaigns will increasingly be blocked, deleted and marked as spam.

The consequence: your email reputation drops drastically.

You are no longer seen as a trustworthy sender and your e-mails are either intercepted directly by the filters of the Internet service providers or end up in the corresponding spam folders.

Tip:You can find out about your sender reputation yourself online. On various pages you can have your IP checked and thus find out whether it is currently on various spam lists. Here is a selection of pages:

Checklist: How to improve your deliverability

In the following, let's take a look at the aspects that are decisive for your deliverability

Technical facilities
Verify your domain using SPF, DKM and DMARC
Link your email address to an active website
Avoid free web-based email addresses like @gmail, @hotmail, @yahoo etc.
Avoid noreply @ email addresses
If necessary, send via a dedicated IP address
Guarantee good data quality
Do not buy email addresses and contact lists from third parties
Use the double opt-in procedure
Delete inactive recipients
Remove bounces
Compose the email
Write really good email subject lines
Avoid spam words
Pay attention to the correct text-image ratio
Send your emails regularly
Run spam tests

Checklist: Measures to be taken against the spam folder

That's a lot of things to consider, aren't they? But don't worry, we will go into each and every one of them and show you how you will achieve the best possible delivery rate.

Technical facilities

It all starts with the right technical settings for sending your e-mails. Here you lay the foundation for the optimal deliverability of your campaigns.

For this reason, it is important that you set up your authentication as a trustworthy sender with your e-mail service provider correctly as a first step.

In most cases, you have three possible authentication systems at your disposal, which let the Internet service providers (Gmail, Yahoo, GMX, etc.) know that the incoming e-mail was sent by an authorized system.

In the following, let's take a look at these security protocols that will help you to be considered a safe e-mail sender.


The Sender Policy Framework ensures that the sender's server is identified.

For example, if you send your campaigns via an e-mail marketing provider such as Mailjet, the Internet service provider of your recipients will be able to ensure, thanks to the SPF, that the e-mails are not viewed as spam, as the sending server is regarded as safe.

Set up SPF at Mailjet


DKIM stands for “Domain Keys Identified Mail”.

It adds a unique signature to your mail, which is assigned to your domain and used for all messages you send.

This helps the Internet Service Provider to control the authenticity of your e-mails and guarantees the integrity of your messages.


DKIM setup at Mailjet.


To protect your domain even better against phishing attempts, DMARC (Domain-based Message Authentication, Reporting & Conformance) can be used in combination with SPF and DKIM.

The aim is to prevent fraudulent phishing emails. These use almost identical sender addresses and pretend to be a trustworthy company in order to obtain sensitive customer data.

Many Internet service providers have changed their security precautions so that unauthenticated e-mails are rejected before delivery.

The Domain-Based Message Authentication Reporting and Conformance (DMARC) an email validation system to act against techniques often used in phishing and spam emails, such as emails with fake sender addresses that appear to come from legitimate organizations.

You can find out how to set up your sender domain at Mailjet here: SPF & DKIM authentication.

It is therefore particularly important that you use the correct sender address. We'll look at what that should be in the following.

Specify the IP address

Just as banks use Schufa to determine a creditworthiness, the ISPs (Gmail, Yahoo, etc.) assign a reputation value for each IP address of the sender.

A distinction must be made between 2 different types of IP address: The shared IP and the dedicated IP.

Shared IP

Much depends on your email volume. If you send a few hundred or thousand mails per month (bulk e-mail), it makes sense to use a shared IP address. Here you send with other users via an IP and benefit from the good reputation.

Your advantage: It is particularly difficult for senders with low volumes to send and maintain a positive reputation. A shared IP address helps you to still achieve optimal deliverability.

Difference between shared and shared IP addresses

However, the “caught up, caught up” principle also applies here. If other e-mail senders who send from the same pool are joking and are punished for this by ISPs, then you will also be affected.

Dedicated IP

A separate IP address is particularly interesting for frequent senders. If you send enough emails (we recommend at least 150,000 emails per month or more), you no longer have to rely on the reputation of other senders.

With a dedicated IP you have sole control over your email reputation. It also means that negative statistics will affect your deliverability very quickly.

Since you do not have to share the IP address or the technical resources with other senders, you are able to send larger amounts of e-mails in less time.

But a dedicated IP address is not always worthwhile. Sometimes a shared IP address is sufficient. You can find out which variant is right for you here: The difference between dedicated and shared IP.

The correct return address

In addition to the subject line, your recipients will also see the name of your sender address first when they search their inboxes for important and interesting new emails.

But in order for your e-mail to make it this far, it is important to consider a few when choosing your address.

Do not use private email addresses from Gmail, GMX or Web.de, this practice seems unprofessional and with increased sending volume your e-mails will probably be intercepted by every spam filter.

Verify your domain. Therefore, only use a suitable address that is linked to your website.

Example: confirmation of a domain

This increases your chances of being viewed as a trustworthy sender by the Internet service providers of your recipients.

tip: Use your brand name after the @.

This creates a clear assignment of your e-mails. Free web-based e-mail addresses such as @gmail, @yahoo, @web, @hotmail etc. are particularly popular with self-employed and small businesses.

Nevertheless, avoid such e-mail addresses.

Regarding the information before the @, the following applies:
Before either, choose a non-personal sender name such as

If you are a sole trader and only have one post box, a combination of your own and company name is a good idea.

Example of different email addresses in the Mailjet backend

If you appear as a personal brand, only your own name is conceivable.

Another still widespread mistake is using a so-called “noreply address” - whether for marketing or transactional emails.

These e-mails usually contain automatically generated information to which the recipient should not reply. If he does, the answers usually come to nothing.

E-mail communication appears impersonal and unwanted here. Such e-mail sender names give the impression that the sender does not want a response from the recipient.

This can be problematic under certain circumstances.

Example of a Noreply email
In the case of marketing emails, it appears as if the company “only” wants to place its advertising and is less interested in a real exchange with the recipient.

How you are a better partner for your customers and which addresses we recommend, we have put together for you in this blog article.

Guarantee good data quality

The basis of every successful e-mail campaign and profitable e-mail marketing is the contact list.

Contrary to the widespread opinion that “a lot brings a lot”, the more contacts you have in your list, the more valuable it is. Sending as many e-mails as possible to many collected e-mail addresses is neither worthwhile nor legal.

It is better to send to a loyal and interested target group that has signed up for your newsletter out of their own interest.

This practice will also improve your e-mail deliverability, as your contacts will register with active e-mail addresses.

In the following, let's take a look at what makes an optimal registration process and which special aspects need to be taken into account.

Receive email addresses

DSGVO-compliant registration and deregistration

In the last year, you probably couldn't avoid having to deal with the subject of the GDPR.

In addition to important rules for data backup and protection of privacy, the new regulation also brought a lot of work for the e-mail marketing area.

So that you are on the legally safe side, you should absolutely note two important points:

  1. Use a double opt-in widget for the registration process for your newsletter
  2. Provide an unsubscribe link at the end of every newsletter sent

Double opt-in means that the respective contact receives an email after registration in which this step has to be confirmed manually again.

Example of a confirmation email for a double opt-in procedure

Many e-mail service providers such as Mailjet already provide you with the functions you need, so that you only need to adapt these registration forms to your own design.

The widget gives you the advantage that the registration of the new contact is automatically saved and you can simply download this proof for your records.

With Mailjet, you can create your very own widget with just a few clicks

At least as important as signing in is the ability to unsubscribe from your contact list for your recipients.

If you do not offer this option, you run the risk of being marked as spam or blocked. Both of these damage your email reputation and thus also your deliverability. This must be avoided at all costs.

We have prepared a detailed article for you here about the optimal unsubscribe process.

Important: The more conscientiously you maintain your contact list, the more this will have a positive effect on your email deliverability. So it's worth it! ;)

Buy third party email addresses: yes or no?

In principle, it is important not to buy, borrow or copy email contact lists from third parties.

Using lists like this is a waste of money.

These lists contain many spam traps and poor quality email addresses. The use of such e-mail lists also violates the sending guidelines of numerous e-mail marketing software.

The probability that these e-mail addresses are already known to the spam filters is high.

If your email is sent to this address, it will automatically be considered spam.

If the e-mail list contains several such e-mail addresses, then you have a problem. So keep your hands off it.

Also with Mailjet: The correct construction of the contact list is mandatory.

Maintain the email contact list

In order to be able to maintain your contact list in the best possible way and to remove inactive contacts, you need an insight into your e-mail statistics.

A positive e-mail reputation and good deliverability can only be guaranteed with a well-maintained contact list, the prompt removal of inactive contacts and the sorting out of unsubscribed recipients.

In your statistics, you should therefore keep an eye on your last email campaign in order to keep it up to date.

In the following, we will show you the most important aspects that you should definitely consider when evaluating your campaigns:

  • Bounced means that you can no longer reach a recipient at his or her address. If an e-mail is not delivered because this account no longer exists, it is considered to be “bounced”.
  • Unsubscribed means that a recipient has chosen to no longer receive their emails. He ends the subscription and ends up in the unsubscribed category.
  • Blocked are e-mails that were previously referred to as "bounced" because the e-mail address no longer exists. However, you have not revised your contact list and tried again to send an e-mail to this address. Mailjet has already flagged this no longer existing address. The email is considered to be “blocked”.
  • Spam: If one of your contacts marks one of your e-mails as spam, future messages that you send to this address will also be directed to the spam folder. This will have a negative impact on your statistics as your spam rate will increase. We also add emails to this category that get caught in a spam trap (incorrect email addresses that anti-spam providers use to identify the relevant senders) or for which there have been complaints ( if a recipient has marked a normal e-mail as spam).

Select which statistics should be displayed with one click

tip: With Mailjet you can have the individual statistics displayed with the corresponding e-mail addresses.

In this way, you can easily and quickly manually unsubscribe addresses with the status “bounced” or “blocked” from your contact lists and thus improve your statistics.

If you maintain your contact lists regularly, you will have little effort and will achieve better results as a result. This ultimately benefits the deliverability of your emails.

Compose the email

The right coding

Variant 1: HTML

Many providers of e-mail marketing solutions offer you the option of programming your e-mails directly using HTML in addition to the drag-and-drop editor.

But be careful: an incorrectly encoded e-mail can quickly trigger the anti-spam filter!

So make sure that there are no programming errors in your HTML code.

tip: If you are unsure about programming your e-mail, simply use Mailjet's e-mail editor, it will generate an optimized code for you.

Variant 2: MJML

In addition to the drag-and-drop editor and the option of creating your e-mails via HTML, Mailjet also offers you another alternative: our own MJML programming language!

With this you can create appealing e-mail templates that are optimally displayed on all end devices.

Easily encode emails with MJML

MJML stands for “Mailjet Markup Language” and was specially developed to make responsive e-mails even faster and more effective.

You can use our open source programming language both online and offline, give it a try!

Avoid spam words

There is probably not much that is more frustrating for email senders than finding important campaigns in the spam folder.

If you follow the technical basics, clean your contact list regularly, and send valuable content, your emails have a good chance of not being sorted out by spam filters.

Another important criterion when classifying your e-mails using these filters is the level of “spam words” it contains.

Which terms should you avoid to improve your deliverability?

In general, there are a few topics that spam e-mail senders like to use, especially:

  • Gambling
  • Shopping
  • health
  • Dating
No jokeStrike nowStop hair lossFind a partner
No rip offSpecial dealCelluliteSexy men / women
Redeem profitLimited timeSlightly lose weightGet to know singles
pokerbargainRemove wrinklesDream man / woman
betAvailable today onlyMiracle healingfetish

Table: Examples of spam words in emails
But it's not just in these industries that you should pay special attention to what words you use in your email and subject line. There are many terms that can get you spam filters 'attention because your content is similar to spammers' practices.

We have put together a detailed list of suspicious words for you in our free guide:

Perform a spam test

Spam tests help you to determine the spam risk of an e-mail.

If you use an email service provider like Mailjet to send emails, then your best choice is what is known as a seed list. A seed list is a list of internal emails that you can send a test email to, e.g. to coworkers, family members, or friends.

Ideally, the email address covers a range of email clients and devices. This is a great way to check whether or not your email is likely to make it through the various spam filters.

Spam testers test your email for:

  • E-mail server reputation
  • Sender email address
  • Send IP address
  • E-mail server configuration
  • Email content and subject line
  • IP blacklisting

Text-image ratio

Pictures make e-mails lively, colorful and contain a lot of information. Therefore, it is tempting to use a variety of images.

But is this practice recommendable?

The answer is no. E-mails that contain little text and many images are popular with spammers. This is also known to the Internet service providers, who consequently block such e-mails.

Would you like to try out the template? Create a free account to view and download this newsletter template.

We therefore recommend a text-image ratio of 60:40 or even 70:30 in favor of the text. To learn more about making the best use of images, check out our blog article on the subject.

Send your emails regularly

Spam filters suspect irregular sending of e-mails.

The more regularly you send e-mails, the better the e-mail clients will get to know you and the faster you will be classified as a trustworthy sender.

The risk of your e-mails getting into the spam folder is reduced accordingly.

But be careful! Regularly doesn't mean you should bombard your recipients with email. Install a fixed delivery frequency and time. At Mailjet, for example, we send our newsletter every Thursday at noon.

But does that mean that you should stop special mailings now? No. However, try to always send marketing e-mails that are firmly planned in the editorial plan (newsletters of all kinds, e-mails with content triggered via RSS feed, etc.) at the same time.

Example of an email scheduler. Source: Mailjet

The right email marketing software

After the technical and content basics, one important aspect remains that contributes significantly to the deliverability of your email campaigns: Your email service provider.

These providers provide you with the infrastructure for sending your e-mails, which makes the choice particularly important.

So first check what requirements you have of your provider and whether they can be met.

Let's take a look at the various functions that you should definitely pay attention to and why they are so important for your email dispatch (and for your deliverability):

Function:Why it matters:
SPF, DKIM & DMARCThe technical basics of your shipment
Dedicated / shared IPImportant for the different requirements of customers
Full GDPR complianceSo that your e-mails are sent in accordance with the latest data protection guidelines
Reliable SMTP serverFor sending your emails quickly and reliably
Detailed email statisticsFor the analysis and optimization of your campaigns
Easy to use email editorFor creating your emails quickly and easily
segmentationImportant for your personalization and the organization of your contact lists
A / B testsTest different variants of your emails for the best result

Table: Your email marketing software should have these functions

Make sure that your provider complies with the European data protection guidelines. Appropriate certificates such as ISO 27001 are a good indication of this. They guarantee that your e-mail software has been checked according to international standards and meets the requirements.

Get more tips and tricks in our 32-page guide for optimal deliverability and how to implement this for your email marketing:

Click here for the free guide to optimal deliverability


You now know how to lay the best possible basis for good e-mail deliverability - from the technical settings to the optimal content design of your e-mail campaigns.

However, it is also true that you will not achieve a satisfactory deliverability rate without your own dedication. Maintaining your contact lists is a constant process, which, if implemented correctly, will reward you with correspondingly positive results.