Most of your subscribers will open your email on their phone, by a wide margin. Which means if your email only looks great on your desktop, it doesn't look great where it counts.
Good news: every Constant Contact template is mobile-responsive by default, so the layout adapts automatically. But responsive doesn't mean foolproof, there's still plenty you can do that makes the mobile experience worse.
Here's a quick check you can run in about 5 minutes.
1. Subject line under 40 characters
Phone inboxes cut off long subject lines aggressively. CC recommends staying under 40 characters (spaces included) so the whole thing shows up in the inbox preview.
Quick test: Count it. If it's over 40, cut a word. If it's still over 40, cut another.
2. Body text at 14pt, headlines at 22pt minimum
Tiny text forces people to pinch-zoom, and most won't bother — they'll just close it. We recommend 14pt for body text and 22pt for headlines at minimum, and sticking to web-safe fonts so your design holds up across devices. No more than two different fonts in the whole email.
Quick test: Open your draft, zoom out so it's about as big as a phone in your hand, and try to read it. If you're squinting, increase the size.
3. 20 lines of text or fewer
Here's the stat that should change how you think about email length: We analyzed 2.1 million customer emails and the ones with 20 lines of text or fewer saw the highest click rates.
Quick test: Count your lines. If you're over 20, the answer isn't a smaller font, it's a Read More block pointing to the full version on your site.
4. 3 images or fewer, all with alt text
Emails with 3 or fewer images and 20 lines of text were the top click-rate performers. Mobile users often disable image auto-download to save data, so your beautifully designed image-heavy email might show up as a bunch of empty boxes. Alt text is what saves you in that scenario.
Quick test: Count images. Add alt text to every single one.
5. One clear CTA — and make it a button, not a link
Buttons are 25% more likely to be clicked than text links. Why? Buttons are big, obvious thumb targets. Links are skinny. Tap targets matter on a 5-inch screen.
Also: keep it to one primary CTA. Multiple CTAs on mobile = decision fatigue.
Quick test: Pick your most important action. Make it a button. Make any secondary action a smaller text link below it (if at all).
6. Logo sized to 150–200px wide
Images 480px wide or larger fill the entire mobile screen. So if you uploaded a 1200px-wide logo, congratulations, your logo is now the entire first screen of your email and your headline is below the fold.
Quick test: Resize your logo to 150–200px wide before uploading, or use CC's resize-in-editor option.
7. Preview & Test — before you ever hit send
There are three ways to do this in CC, all from the editor:
Preview & Test button — shows desktop and mobile renderings side by side
Send a test email to yourself — open it on your actual phone, in dark mode if you can
Inbox Preview — shows how your email looks in the top 5 inbox clients on both desktop and mobile
TL;DR — the 5-minute mobile pre-flight checklist
Subject line under 40 characters
14pt body / 22pt headlines minimum
20 lines of text or less
3 images or fewer, all with alt text
One CTA, as a button
Logo at 150–200px wide
Preview & Test on desktop, mobile, and Inbox Preview
