Images can be blocked for many reasons. Certain e-mail clients will block images by default as a security caution (many spammers would send e-mails with only images — no text). There are plenty of ways to get around this, and ensure your e-mail campaigns look spectacular throughout all clients.
Alt Text –
This is the easiest, quickest and simplest way to defeat image blocking. Alt text (alternative text) is what’s displayed to the user if images haven’t loaded. Images can fail to load for several reasons; perhaps the image quantity is too high and has been blocked as a security precaution against spammers (image only emails are commonly related with spam). It could also be that your image sizes are too big, therefore the e-mail client hasn’t been able to download them. Finally, it could simply just be the client that your subscribers are viewing your e-mail on. For example; Outlook 2000–2013 blocks images by default, and Outlook/Outlook.com is currently used by 8.8% of all e-mail users.
Your ALT text should be informative of the image it’s replacing. This is especially important for e-commerce marketers, if you’re selling products be sure to leave a short description and maybe a price so that the customer is still intrigued to the product without an image automatically displaying.
You can also style your alt tags to help fit in with the house style of your brand and e-mail design. You can align the text, also change the colour, font family, font size and font weight.
It’s best practice to keep it short. You initially have included images to portray something graphically, and keep the reader interested, therefore you don’t want to bore them with lines and lines of descriptions of what your image was. Try and prompt them to turn their images on!