New function – embed images into newsletters

With the long-awaited embedded images function, it is now possible to embed images into your emails. It is possible to send images up to 50 KB in size and ensure that these images are displayed straight when the recipient opens the email.

Embedded Images


The embedded image is sent in an attachment as a base64 encoded image. When the newsletter is opened, the image is immediately downloaded and displayed. These images offer advantages that inline images do not. Inline images are embedded directly into the email and not sent as a MIME attachment. This increases the size of the source code and this, in turn, increases the risk of the email being classified as spam.

Find out here exactly how this new function works and what the advantages and disadvantages are.

How do embedded images work?

The selected images are transformed into text format by means of base64 encoding. A content ID (cid) is then attributed to the image, which makes the image in the email available as a reference, so that the image can be embedded as soon as the email is opened. Because the image is sent as text, the graphic is available straight away and can be loaded in the email program. Most email programs and clients recognise the encoded images and convert them back into graphics.

What does the new function do for you?

The use of an embedded image means that a company logo, for example, can be displayed straight away and does not need to be loaded.

This is useful because in most email clients, such as Outlook, Thunderbird and Gmail, the recipient must allow the images to be be displayed. So if the images are embedded, this process is avoided and the images are shown immediately.

The use of embedded images works with Newsletter2Go in almost all browsers and email clients. The exceptions are: Microsoft, Hotmail and Yahoo Mail.

This all sounds fantastic, but there are some disadvantages. The most notable disadvantage is the increase in the size of the source code. Images that are sent as encoded text change the size of the email. The size and quantity of the images affects the size of the data sent, because the memory required for the text of the image is often greater than the size of the image itself.

This example logo below would require an entry in the source code of more than 2000 characters.

Inline Images

An increase in data size yields an increase in the time required to load the email. And because the images are embedded, the recipient is forced to download them. So it is not really a surprise that emails sent with embedded images are sometimes a source of annoyance, in particular for mobile device users with a limited data download allowance.

It is also worth noting that the increase in email size not only affects the download time but also increases the probability of the email being categorised as spam.

How do I use this new function?

The embedded images function comes as standard with every account and is extremely easy to use. When you have selected the graphic that you would like to embed, check the box on the bottom right for ‘Embed image’. But be aware that this function will only work with images that are smaller than 50 kilobytes.

Embedded Images


Once you have checked this box and clicked on ‘insert image’, the image will automatically be encoded as base64 and added to the newsletter. Try it out now!

The differences made clear

It is time for us to show you what the difference actually looks like. The top image shows an email without embedded images that has been opened in Thunderbird. By contrast, the email below shows embedded images at the top and on the left, and a normal, non-embedded image on the right, which has not loaded. It is also shown in Thunderbird.

Thunderbird No embedded images

Thunderbird embedded images

Our Recommendation

Because of the increased risk of spam categorisation and the decreased delivery rate that this may incur, we recommend using embedded images sparingly. And the increase in data size is also not an insignificant point.

We therefore recommend that you proceed with caution when using embedded images, if at all. Limit yourself to 1 embedded image per email and make sure that that image is the most important, e.g. a company logo or a button to confirm subscription to a newsletter. An embedded company logo will quickly allow the recipient to identify the sender and this may increase interest in the email itself.

We advise that you do not use multiple embedded images in a single email as this will increase the risk of the email being classified by spam.

If you have any suggestions, criticisms, ideas or needs with regards to any of the Newsletter2Go software features, please get in contact with us. We will endeavour to take your comments on board when developing our product.

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