Short
Under 45 characters
Most phones cut longer subject lines. The tool flags the long ones.
A subject line people open because it looks written for them.
Say who you write to, what you offer and, if you have one, a true detail about them. You get subject lines grouped by approach, with their length and what might make them look like an ad.
Runs in your browser. Nothing you type leaves the page.
Fill in who you write to and what you offer to get subject lines.
01What gets opened
A subject line sells nothing: it earns the first line a read.
A stranger decides in a second, often on a phone. Subject lines that work look like something a colleague would send.
True
A detail about them
A town, a project, a service they offer: one accurate detail proves the email is not a mass send.
Plain
No capitals, no promise
Capitals and words like “free” or “offer” make an email look like a promotion. The tool flags them.
Follow-up
A different subject
A follow-up can pick up the thread, or ask plainly whether to keep writing — often the one that gets a reply.
Read more: Cold email subject lines that get opened · Objet d’email de prospection (FR) · Check the whole email
02Questions
What people ask.
How long should a cold email subject line be?
Aim for under 45 characters, four to seven words. Most mobile mail apps cut beyond that, and a short subject reads more like a message between people.
Should I put their first name in the subject?
It isn't needed. A true detail about their company convinces more than a first name, which every sending tool inserts automatically.
Are the subject lines sent anywhere?
No. They are built in your browser from patterns; nothing you type leaves the page.
Does a good subject line keep me out of spam?
No. Placement depends mostly on the sending domain's reputation and how recipients react. A plain subject only avoids looking like a promotion. Check your domain with the free domain check too.
Should I test several subject lines?
Yes, if you send enough to compare: change one thing at a time and judge by replies rather than opens, which are poorly measured since mail apps prefetch images.
03Free tools
More free tools.
French company searchDescribe a trade, pick a département and a size: how many active companies the French register lists, and ten of them.Open the toolFrench company lookupA name, a SIREN or a SIRET: what the register publishes — activity code, head office, creation date, size, leaders.Open the toolDomain checkSPF, DKIM, DMARC and MX read from DNS, with what each one means and what to fix.Open the toolCold email checkerPaste a first email: length, links, pressure words, the question, the way to say no — in English or French.Open the toolSPF record generatorTick the services you send through and get one valid SPF record, inside the 10-lookup limit.Open the toolDMARC record generatorPick a policy and a report address; get the record and where to put it.Open the tool