Free email marketing tools
Check your subject lines and emails before you send. No sign-up, nothing stored.
What the free tools check — and what to do next
The two free tools here check an email before it reaches anyone’s inbox. The subject line tester scores a subject and its preview text out of 100 and shows how they will look on a phone and a desktop. The spam checker reads a whole email — subject plus HTML or plain text — and gives it a spam score out of 10, with a checklist of what filters tend to penalise.
Both run on the spot without an account, and nothing you paste is saved. They use the same checks that run inside MailNesto before every campaign, minus the parts that need to know your sending domain. Treat them as a second pair of eyes: a clean result removes common mistakes, but inbox placement also depends on things no text checker can see.
What the subject line tester checks
Type a subject and, ideally, the preview text. The tester fills any merge tags with a sample value, so {{first_name|there}} reads as “Priya”, then checks length, word count, capital letters, punctuation, emoji, common spam phrases, personalisation, numbers and the preview text. Each check comes back as a pass, a warning, a fail or a tip. The score starts at 100 and loses points for each problem.
The inbox mock-ups cut the subject where real inboxes do: about 38 characters on a phone and 68 on a desktop. If your offer sits at the end of a long subject, you will watch it disappear behind the ellipsis.
- Length: 15 to 50 characters passes; 51 to 70 is a warning; over 70 is a fail
- Capitals: more than about a third of the words in CAPITALS is a fail
- Punctuation: doubled exclamation marks, question marks or dollar signs are a fail; two or more exclamation marks is a warning
- Honesty: “Re:” or “Fwd:” on a campaign is a fail
- Merge tags: {{first_name}} without a fallback is a warning
Using your score to write better subjects
Scores of 85 and above are graded Great, 70 to 84 Good, 50 to 69 Fair, and anything lower Poor. Fix fails first: they cost the most points and are what filters and readers react to. Warnings are judgement calls — a 58-character subject for a detailed course announcement can be fine if the key words come first. Tips are suggestions, not faults.
A score measures avoidable risks and clarity. It can’t tell you which of two good subjects your audience prefers. For that, send both to a small share of your list with an A/B test in MailNesto and let opens or clicks choose the winner for everyone else.
- Lead with the specific: “Your Pune workshop seat is confirmed” beats “Important update”
- Make sure the email delivers what the subject promises, on the first screen
- Use preview text to add a second fact rather than repeat the subject
- Keep urgency for real deadlines, so “last 48 hours” is believed when you use it
- Write for the phone first and check where the tester cuts the line
What the spam checker looks at
Paste the subject and either the HTML of your email (most tools can export it or show its source) or the plain text. The checker strips the markup and looks for trigger phrases across the subject and body, then inspects the HTML itself: how much text sits beside the images, missing alt text, the number of links, unfinished links, URL shorteners, scripts or forms, and the total size.
Each problem adds points, up to a maximum of 10. Below 2 reads “Looks good”, 2 to 4.9 “Needs a few fixes”, and 5 or more “Likely to be filtered”. The unsubscribe-link and postal-address checks are shown as warnings, because many platforms add both at send time, but they still add to the score. Make sure yours does add them.
Fixing what the checker flags
Most flags come from templates and copy-paste rather than your words. Fix fails first, then run the check again.
- Unfinished links: social icons left at “https://” or “#”, or example.com placeholders. Fill them in or remove the icon
- Shortened links: replace bit.ly-style links with the full address, since hidden destinations look suspicious
- Too little text: an email that is one large image and a single line needs a few real sentences describing the offer
- Missing alt text: describe each image (“Diwali hamper with dry fruits, ₹1,499”) so the email makes sense with images off
- Over 102 KB: trim the HTML by removing markup pasted from word processors and repeated styles; linked images don’t count towards it
- “Click here”: use link text that says where it goes, such as “See the menu” or “Book your seat”
What no content checker can see
Mailbox providers decide mostly on who is sending and how recipients respond, not on wording alone. A perfect score will not rescue an email sent from an unauthenticated domain, to a purchased list, or to addresses that bounced last month. Gmail and Yahoo expect bulk senders to authenticate with SPF, DKIM and DMARC, offer one-click unsubscribe and keep spam complaints low.
Inside MailNesto, the spam check also tells you whether your From domain is verified, so the email is DKIM-signed. Pair it with list cleaning, the warm-up ramp for new domains and an inbox placement test before a big send such as a Diwali sale or an admissions announcement.
Questions about the free tools
Is anything I paste into these tools stored?
No. Each check runs when you submit it and returns the result; nothing is saved to an account or a list. To prevent abuse, each tool allows a limited number of checks per minute from one connection.
Why did my subject score change when I added preview text?
An empty preview text costs points, because inboxes fill the gap with the first words of the email, often “View in browser”. Preview text that simply repeats the subject is marked down too. Anything under 25 characters gets a tip to say more.
Why does the tester show a name instead of my merge tag?
It fills merge tags with sample values — a first name as “Priya”, a city as “Hyderabad” — so the length and preview reflect what a real person sees.
Can I check emails written in Hindi or another language?
Yes. Length, punctuation, emoji, links, images and size are checked in any script. The spam phrase list and the capitals check are written for English, so read a Hindi or Tamil subject once as a recipient would. Vowel signs are counted as separate characters, so the count may run slightly longer than it looks.
How large an email can the spam checker take?
Up to about 300,000 characters of HTML or 100,000 of plain text, with a subject of up to 300 characters. If your HTML is over 102 KB, Gmail will clip it anyway, so trimming it helps twice.
Does the check inside MailNesto do more than the free version?
Yes. Inside the app it also knows your From address and confirms whether that domain is verified for DKIM signing, and where the platform runs SpamAssassin, its score is shown alongside the checklist.