Free tool for List
Write your subject and preheader, then see exactly how they render in Gmail, Apple Mail, and Outlook on every screen size. Catch truncation, spam signals, and weak preheaders before you hit send.
55 charactersAim for under 46 for mobile safety
70 charactersAround 85 to 100 across most clients
Spam signal check
No obvious spam signals detected.
Inbox previews
Distinctful
The next post is the one that pays back the last twelve
A short framework for choosing which idea to actually write this week.
Distinctful
The next post is the one that …
A short framework for choosing which idea to actually write this …
Distinctful
The next post is the one that pays back the last twelve
A short framework for choosing which idea to actually write this week.
Distinctful
The next post is the one that pays back the la…
A short framework for choosing which idea to actually write this week.
Distinctful
The next post is the one that pays back the last twelve
A short framework for choosing which idea to actually write this week.
Distinctful
The next post is the one that …
A short framework for choosing which idea to actually write …
Each mail client truncates the subject at a different width. These are the practical cutoffs based on 2026 layouts at default zoom.
| Tier | Range |
|---|---|
| Gmail desktop | About 70 characters before truncation |
| Gmail mobile | About 30 characters in portrait view |
| Apple Mail desktop | About 55 characters |
| Apple Mail mobile | About 46 characters in portrait |
| Outlook desktop | About 60 characters |
| Outlook mobile | About 30 characters in portrait |
| Preheader | 85 to 100 characters across most clients |
Open rate is mostly about three things, in order: the sender name, the subject line, and the preheader. Most operators obsess over the subject and ignore the preheader, but the preheader is where you finish the sentence the subject started. Keep the subject under about 46 characters so it survives every mobile inbox, write the preheader as the next line of the email instead of a duplicate, and avoid the obvious spam signals like all caps, multiple exclamation marks, and dollar signs. Past that, the right test is not the tool. It is sending two versions to a small slice of your list and seeing which one actually opens.
Around 40 to 50 characters. That fits inside almost every mobile inbox without truncation. Shorter is fine. Longer is fine if the part that matters is at the front. The point is not the length itself, it is whether the subject still works after the inbox cuts it.
Yes, more than most operators think. The preheader is the second line in the inbox preview on most clients. Wasting it on the same words as the subject is a missed open. Writing it as the actual next sentence of the email is one of the highest-leverage habits you can build.
Not inherently. A single relevant emoji can pull the eye in a crowded inbox. Two or more emojis usually look like spam. The honest test is whether the emoji adds information or noise.
All caps in the subject, multiple exclamation marks, dollar signs in the subject, FREE in the subject, and aggressive urgency phrases like ACT NOW. None of these will guarantee a spam folder hit on their own, but stacked together they raise risk and almost always lower the open rate from real humans.
The connected platform that runs your content business
Distinctful List connects subject line performance to the subscribers who clicked, the offers they bought, and which writing earned the result.