Type a subject line and see where each inbox cuts it off. Gmail on a phone shows far less than you think — about half of what the desktop shows.
Where each inbox cuts off
There is no single character limit. Every client truncates at a pixel width, so a subject full of Ws dies sooner than one full of is. These are working approximations at default settings and typical window sizes:
| Where | Roughly visible |
|---|---|
| Gmail, desktop browser | ~70 characters |
| Gmail, Android and iOS app | ~35–40 characters |
| Apple Mail on iPhone | ~35 characters |
| Outlook, desktop | ~60 characters |
| Outlook.com in a browser | ~60 characters |
The number that matters is the phone one. Most email is opened on a phone, so write for 35 characters and let the rest be a bonus. If your subject only makes sense once the reader sees all 70, it does not work.
Front-load the thing that matters
"Following up on our conversation about the March invoice" becomes "Following up on our conv…" on a phone, which says nothing. "March invoice — following up" survives the cut with the meaning intact.
The test is simple: cover everything after the 35th character and read what is left. If it does not tell the reader what the email is about, reorder it.
Preview text is free space you are probably wasting
The grey line after the subject is the first text in the email body. If your email starts with "Hi Dana," then that is what shows — you have spent a whole line of inbox real estate on a greeting. Put the useful sentence first, or set the preheader deliberately.
What actually gets ignored
Length is not usually why a subject fails. These are:
It reads as marketing when it is not. ALL CAPS, exclamation marks and "FREE" make a one-to-one email look like a campaign, and get treated like one.
It is vague. "Quick question" and "Touching base" tell the reader nothing about whether to open now or later, so they choose later.
It repeats the thread. Six replies deep, "Re: Re: Fwd: Project" is invisible. Change the subject when the subject changes.
The follow-up you actually forget
A good subject gets the email opened. It does not remind you that you sent it eight days ago and nobody replied. That is the job Simple CRM for Gmail does — notes, follow-ups and tasks attached to the person you sent it to, in the Gmail sidebar. Fourteen days free, no card.