To include HTML images in email signatures like a company logo or social media icons, you have two image options available. You can either embed an image directly into the email signature template or host it externally and link to it.

Most email clients can display images in email signatures without any significant issues. However, when creating a signature template, there are benefits to choosing one method over the other.

Email platform/service	Embedded images	Hosted images
Microsoft 365 (Office 365)	No	Yes
Google Workspace (G Suite)	Yes	Yes
Exchange 2019	No	Yes
Exchange 2016	No	Yes
Exchange 2013	No	Yes
Exchange 2010	No	Yes
Exchange 2007	No	No
Exchange 2003	No	No
Outlook 2019	Yes	Yes
Outlook 2016	Yes	Yes
Outlook 2013	Yes	Yes
Outlook 2010	Yes	Yes
Outlook 2007	Yes	Yes
Outlook 2003	Yes	Yes
OWA (Outlook Web App)*	No	No
Gmail	Yes	Yes
Outlook.com**	No	No

* To add a linked image, you need to open the image in a browser and copy it into the Office 365 (now Microsoft 365) OWA signature editor.

** You can add a hosted image by adding the HTML source via the signature editor.

How to embed images in email signatures

If you want an image to appear without the recipient having to click a ‘Download Images’ button, we recommend embedding it within the email signature. This is when an image file is attached to an email and referenced using a Content-ID (HTML image tags).

A standard Content-ID will look like this:

<img src="cid:myimagecid" />

When an email client refers to these images in email signatures, they will be displayed automatically. This is because they are referenced in the source of the message.

However, when you add images to email signatures for Outlook, Gmail, and other email clients, the size of the messages increases. This means there is a risk that the images will appear as separate attachments in some email clients. There are also known issues with images being stripped out of emails and increasing in size on iOS devices.

How to host images in email signatures

If you don’t want email signature images to appear as attachments, we recommend saving and hosting them. You can do this on a web server or via a free image hosting site like Imgur or Flickr. They will then be referenced in the email using a web URL. This is known as hosting or linking images:

A hosted/linked image would typically look like this:

<img src="https://cdn.exclaimer.com/Static2/exclaimer-logo_178x36.png" />

By doing this, your images are never a physical part of the email. Instead, they are essentially downloaded into the message every time it is viewed, making the email file size smaller.

It’s also recommended that you add alt text (alternative text) to any image you host. This way, the recipient will still be able to make sense of the image if they cannot view it. Adding alt text looks like this:

<img src="https://cdn.exclaimer.com/Static2/exclaimer-logo_178x36.png" alt="Exclaimer logo"/>

However, when using image hosting for your email signatures, a recipient may need to manually click a ‘Download Images’ button for the images to display. This is a way of protecting the recipient against possible viruses.

Which option should I choose to show images in email signatures?

You need to consider how your customers/clients view the emails you send them. If many use email clients like Outlook, embedding images in email signatures is recommended. However, you should use hosted imagery if you know that many recipients will be viewing your emails on mobile devices.

Of course, if you don’t want to ever have to worry about which option you should choose, use an email signature generator/solution.