Email Subject Line Tester.

Only if the email really is a reply or a forward. Google's sender guidelines say not to send messages whose subject starts with Re: or Fwd: unless they are actual replies or forwards, and Yahoo's ask senders not to use deceptive subject lines. In the US, the FTC's CAN-SPAM guide says the subject must reflect the content, with no exception for business email. A follow-up that SendCanyon sends in the same thread is a real reply, so tick Follow-Up and the tester treats Re: as honest.

No public list decides it, because filters weigh many signals together, but some words and patterns show up in spam far more than in normal mail. The tester checks your line against our spam-phrase list, covering money, urgency, pressure and similar categories, and suggests plainer wording for each match. With the spam filter check on, it also runs your subject through a real spam filter and shows only the rules your subject adds.

No mailbox provider publishes a rule against emoji, and we found no primary source showing that filters penalise a single one, so the tester reports the count rather than a verdict. An emoji is sent as encoded text, so how it looks depends on the reader's device, and in a cold email it rarely reads like one person writing to another. The tester flags a line with three or more.

You can, as long as every contact has that field filled. SendCanyon fills {{first_name}} for each recipient, and a contact with no first name gets nothing in its place, so "{{first_name}}, a question about Q4" goes out as ", a question about Q4". The tester shows your line rendered for a sample contact and with the field empty, and flags placeholders written in other tools' formats, which would be sent exactly as typed.

Because any score would rest on weights someone made up. A single number hides what to fix and can't tell you which rule a line breaks. The tester lists what it found instead: each finding has a status, the rule or measurement behind it and a fix. If a line comes back with no failures or warnings, nothing we can check is wrong with it.

Yes. After a test, SpirenAI, SendCanyon's AI, rewrites the line using only the findings we computed. Each rewrite is tested again, and it is shown only if it has no failures or warnings, keeps only the merge fields you used and adds no numbers or names. You see how many rewrites were left out. Copy any of them, or test it again as your own line.

Preview text is the line an inbox shows next to or under the subject. In a plain-text cold email it is simply the first words of your message, such as "Hi Maya,". Treat the two as a pair: if the preview repeats the subject, the reader sees the same words twice. The tester measures both on one inbox row and flags repetition.

That is a style choice, and no mailbox provider or standard says lowercase or Title Case changes filtering. What does matter is all capitals: a subject written entirely in capitals matches a rule in widely used spam filters, and the tester flags it, along with several shouted words in one line. Pick the case that sounds like you writing to one person.

Yes, it is free. When you run a test, we keep the lines, the result, your IP address and browser for 90 days to prevent abuse, and then delete them. Nothing is ever sent to anyone from this page, and rewrites are made only from what you typed and what the tester found.