Unbury Subject Line Checker

Check your email subject line before you hit send — spam trigger words, length, caps and a Gmail-style preview. Free, by Unbury.

You can write the best email of your life, but if the subject line trips a filter, nobody sees it. It lands in Promotions or spam, and from where you're sitting that looks exactly like "my list is dead." This little tool checks your subject line before you send it: — Spam trigger phrases ("act now", "limited time", "100% free" and about 45 more that filters flag on sight) — Length, with a note on where phones cut you off — All-caps words and stacked punctuation, the oldest spam signals there are — Emoji count, fake "Re:" threading, and whether you actually wrote your preview text — A live Gmail-style preview so you see the line the way your reader will Everything runs on your machine. No account, no sign-up, no permissions, nothing leaves the popup. It's a free tool by Unbury (unbury.co). We fix email deliverability for coaches, consultants and course creators — the subject line is the part you can check yourself, so we made that part free.