Email Subject Line Capitalization
Email subject lines do not have one universal capitalization rule; the choice depends on message context and house style. Chicago explicitly distinguishes routine correspondence from more formal organizational mailings, so this guide does not label one case style universally correct.
For ordinary personal or work email, sentence case is a strong default; formal organizational mailings may use title case when that matches the organization’s style.
Key details
Important caveats
Scope Boundary
Chicago explicitly distinguishes routine correspondence from more formal organizational mailings, so this guide does not label one case style universally correct.
Further guidance
Practical Application
Use sentence case as a strong default for ordinary work/personal email. Switch to title case only when an organization or campaign style explicitly calls for it, and apply that style consistently.
Reader Check
Is this an ordinary interpersonal email, or a branded/formal mailing governed by a subject-line style?
Recommendation
For ordinary personal or work email, sentence case is a strong default; formal organizational mailings may use title case when that matches the organization’s style.
Worked Example
Ordinary email: “Updated timeline for Friday”. A branded newsletter may use “Updated Timeline for Friday” if its house style specifies title case.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Capitalization Q&A: email subject lines — CMOS (opens in a new tab)Chicago Manual of Style · Direct style guidance on sentence case versus title case in email subject lines