Specific beats clever
A specific, clear subject line ("20% Off Your Next Facial This Week") generally outperforms a vague, clever one ("You Won't Believe This!") for a small local business's audience — clarity about genuine value tends to win over intrigue.
Keep it short
Many email clients truncate long subject lines, especially on mobile — keep the most important information in the first several words.
Test two different subject line approaches (if your email platform supports A/B testing) on a genuinely important campaign to learn what your specific audience responds to, rather than guessing.
Avoid spam-trigger patterns
Excessive punctuation, all-caps words, and certain spam-associated phrases ("FREE!!!", "ACT NOW") can hurt deliverability by triggering spam filters, in addition to looking less professional.
Never use a misleading subject line that doesn't match the actual email content ("Your appointment is cancelled" as a subject line for a promotional email, for example). Beyond damaging trust, this can violate email marketing regulations around deceptive subject lines.
Personalization helps, used naturally
Including a client's name or referencing their specific service history (where your platform supports it) can improve open rates — but don't force personalization that feels robotic or oddly generic.
Frequently asked questions
Does emoji use in subject lines help or hurt? This varies by audience — test carefully rather than assuming either way, and keep it tasteful and relevant if you do use them.
How important is the subject line compared to the email content? Extremely — a great email with a weak subject line may never get opened. Give the subject line real attention, not an afterthought.