Overview
Before you upload images to your emails in SmartrMail, review these recommendations to make sure they display well everywhere.
General tips
Format: save images as PNG, JPG, or GIF. PNG retains transparency, and GIF allows for animation.
Color mode: use RGB, not CMYK. CMYK is a print color profile and doesn't render accurately online — it can sometimes break uploaded images entirely.
Alt text: add alt text for accessibility and for subscribers who don't automatically download images. It also helps email clients understand your email's content, which can improve deliverability.
File size: avoid overly large images, both in file size and pixel dimensions. Uploads are capped at 5MB (tested: 4.5MB succeeds, 5.5MB is rejected with a "file too big" error), matching the same limit confirmed for page background images. We recommend staying well under that regardless — ideally under 1MB — since some images won't automatically download on mobile devices to save subscriber data.
Definition (retina displays): newer phones, tablets, and laptops pack more pixels into the same physical space, which can make low-resolution images look blurry. To keep images sharp, export them at roughly 2x the pixel dimensions you actually need, then let the email constrain the displayed size to our recommendations below.
Image size: the available width for images depends on how many columns your content is in — see the section below.
Image size for emails
Height: the maximum height for an image block is 800px. Images taller than this will appear distorted if used with the "edge to edge" option.
Tip: if you need a taller image with "edge to edge" enabled, slice it into two images under 800px each and add them as two separate image blocks instead of one.
Width: SmartrMail emails are 640px wide, so size your images with that as the maximum. The number of columns your content is in also affects the recommended width.
Image blocks
Not set edge to edge:
Columns | Recommended image width |
1 column | 600px |
2 columns | 300px |
3 columns | 200px |
Set edge to edge:
Columns | Recommended image width |
1 column | 640px |
2 columns | 320px |
3 columns | 213px |
Image + Caption blocks
Columns | Recommended image width |
1 column | 385px |
1 column (vertical layout) | 600px |
2 columns | 300px |
3 columns | 195px |
Note: if an uploaded image exceeds these recommended widths, we'll resize it within the HTML for display — but the original uploaded file itself isn't resized, so its full resolution is preserved. Not all email clients respect HTML-based resizing, though, so it's best to upload images at the recommended size in the first place rather than relying on this.