One of the most common reasons our customers get in touch with our support team has got to do with problems in using images in their campaigns. In this blog, I highlight some of the common pitfalls (and questions) about using images and show how you can avoid them.

What is a good file name to use?

To ensure all your images can be viewed correctly across different email clients and web-based email clients, you must be careful of how you name your image files.  All files should be named without any empty spaces or non-ASCII characters.  This means “my image.gif” is out, and “my_image.gif” or “my-image.gif” should be used instead.

In eConnect Email, we now automatically replace all spaces with underscores “_” in your image filename when you upload via the built-in file manager, so you don’t have to worry about spaces in your filenames anymore.  However, you should still take note to avoid using non-ASCII characters (such as accented characters like “á” and “ë”) in your filenames to ensure compatibility across platforms.

Always remember to check your campaigns before sending them out.  Make use of the built-in test sending function in eConnect Email to email yourselves to see how your campaigns render in different email clients.  After all, it’s free and you can send as many times as you want, until you are satisfied with the results.

What about the supported image formats?
Do not use other image formats other than GIF (Graphics Interchange Format) and JPG (developed by Joint Photographic Experts Group).  PNG might work on your browser but it is not supported on email clients so never use PNG format for your newsletters.

What is the acceptable file size for my image?
This really depends on the number of images you have in your newsletter.  If you are only using one image in your newsletter, you might get away with 25KB in file size.  But if you have more images, you must remember that all of them contribute to the overall size of your newsletter, and this could pose a problem.  As much as possible, keep the number of images used to a minimum, and make sure each image is optimized to the lowest file size possible (without sacrificing too much on the quality of the image, of course.)

What’s a good rule of thumb?  If your image contains a line drawing (such as in the case of illustrations) or text or big blocks of single colors, the best format to use is the GIF format.  Images using the GIF format can be saved in a maximum of 256 colors but the best compromise would be 128 colors where you will get reasonably low file size with good image quality.  If the image contains only one solid color for the image file, 64 colors would be good enough.  You may not see much difference in file size between 128 and 64 colors but since every kilobyte counts, your newsletter will be less bloated and your subscribers will thank you for it.


Saved in GIF format. File size: 2.78 KB


Saved in JPG format. File size: 17.1 KB

For photographs and images with gradient effects, you should save them in JPG format.  Using this format, images are compressed in terms of percentages.  The recommended compression percentage is 60%, but feel free to experiment with compression percentages as far as 80%, because your mileage may vary depending on the actual content of your image.


Saved in JPG format with 60% compression. File size 20.2 KB


Saved in GIF format with 128 colors. File size 29 KB

Finally, this is the tricky part for most of you.  If you have a photograph with text on top of it, what is the best format to use?  I would recommend using JPG format and experiment with the compression percentage.  Do note that lower compression percentages will usually cause bubble-like artifacts to appear around the text, so do opt for the lowest compression percentage that you can go before these artifacts start showing up.

If you are planing to use animation, the only format you can use is the GIF format.  Do not try to create an animation in Flash (.swf – even though Flash animation gives you smaller file size comparing to GIF format animation) and embed them in your newsletter.  It will most likely get blocked and will not reach your intended recipients.  Finally, unless you are sending your newsletter for printing, always work on a 72 dpi resolutions and not 150 dpi or higher.  If you are sending your newsletter for printing, consider creating a web version of your newsletter just dedicated for this instead, and still use only lower resolution images for your actual newsletter.

About James Trumbly:
Director of Business Development for eConnect Email, an email marketing software company. James enjoys spending time at the beach and traveling in his free time. Follow him on twitter @eConnectEmail