Your email competes in a list view, against roughly forty other rows, at a glance. All the recipient sees is a sender name, a truncated subject, and a snippet of your first line. That is the entire first battle.
Subject lines that survive
- Short: three to six words. Long subjects get cut on mobile at around 35 characters.
- Lowercase and plain, like a colleague wrote it. Title Case reads like marketing.
- Specific to them: a company name, a page, a number.
- No fake urgency, no "quick question" — both are burnt.
Weak vs strong
Weak: Improving Your Company's Digital Presence
Strong: your checkout on mobile
Weak: Quick question
Strong: 4.2MB on your homepage
Preview text is a second subject line
The snippet after your subject is the first words of your email, and most people waste it on "Hi Sarah, I hope this email finds you well." That is 40 characters of nothing in the most valuable space you have. Start with the substance and let the greeting sit on its own line, or drop it.
Try it
Write five subject lines for one real prospect, then check each in the inbox previewer at Gmail mobile width. Keep only the ones that still make sense after truncation.