Email validation · Use cases · Cold outreach
Use case
Reduce your cold outreach bounce rate with Trueguard.
Keep cold email bounces under 2% per sending mailbox. Trueguard's email verification API checks each address before it enters a sequence, with 100 free checks a month.
Before the sequence starts
One request, four possible answers.
Try one address.
The same check your pre-send script would call. 10 free checks a day, no key, and nothing is sent to the address.
Or try
Why does bounce rate burn a sending domain?
Bounces are a reputation signal
Your sequencer pauses first
Small volumes move the rate fast
Gmail tells you to slow down
How do you verify a cold list before a campaign?
Check the list before it goes into Instantly, Smartlead, lemlist or any other sequencer, before the first bounces arrive. Trueguard has no CSV upload and no sequencer app: a short script calls the API once per address and splits the list by status.
Export the list from its source
Check every address
Split by status
Import only the send file
What should a cold campaign do with each result?
The status decides the file. isCatchall and quality.isDisposable tell you why a result is risky.
Status
What it means
Outbound action
The address passed format, MX and mailbox checks. This includes mailboxes on catch-all domains that Trueguard's advanced catch-all detection validated: safe with isCatchall: true.
Add it to the sequence.
Deliverable at the server, but flagged: a catch-all domain where the mailbox could not be validated, a disposable address, or a risky domain.
Keep it out of the main campaign. With isCatchall: true, send it in a small separate campaign or skip it. Drop disposable addresses.
The address will not take mail: bad syntax, no MX record, or the server says the mailbox does not exist.
Remove it from the list and from its source. It would be a hard bounce.
The mail server gave no clear answer.
Keep it out of this send and re-check before the next campaign. Do not treat it as safe.
Four things to know before you run it.
Invalid results are billed
One call per address
Role and free addresses pass
A check is a snapshot
What is a safe cold email bounce rate?
No mailbox provider publishes a bounce limit. The 2% figure comes from sending platforms and cold-email vendors. Amazon SES counts hard bounces only.
| Source | What it says | Type | Read |
|---|---|---|---|
| Amazon SES | Below 2% recommended. 5% or more puts the account under review. 10% or more "might pause" sending. | Sending platform | 10 Nov 2026 |
| Microsoft Dynamics 365 Customer Insights Journeys | Hard bounce limit 8%, preferred under 2%. That product only, not Outlook.com. | Sending platform | 10 Nov 2026 |
| Gmail sender guidelines | No bounce number. Spam rate under 0.10%, never 0.30%. Cut volume when messages bounce. | Mailbox provider | 10 Nov 2026 |
| Yahoo Sender Hub | No bounce number. Spam under 0.3%. "Remove invalid recipients from your list promptly." | Mailbox provider | 10 Nov 2026 |
| Outlook.com high-volume sender requirements, Apr 2025 | No bounce number. List hygiene is listed as a recommendation. | Mailbox provider | 10 Nov 2026 |
| Smartlead blog, 28 Oct 2026 | Under 2% over 14 days is good. 2 to 4% is a warning. Above 4% on one mailbox with 100+ sends is "where the burn starts." | Sequencer guidance | 10 Nov 2026 |
| lemlist blog, 4 Nov 2026 | "Above 15%, stop sending entirely." | Sequencer guidance | 10 Nov 2026 |
Aim for under 2% per mailbox and treat 5% as stop-and-clean. Trueguard publishes this page and sells email verification. Vendor figures were read on 10 November 2026 and can change.
Get a free API key and check 100 addresses from your next list.
When do Instantly, Smartlead and lemlist pause a campaign?
| Tool | What the help center says | Read |
|---|---|---|
| Instantly | Pauses campaigns when the bounce rate exceeds 5%. On by default. The check runs once a campaign has sent at least 200 emails. The threshold can be changed or the feature switched off in Preferences. After a resume, the campaign is not auto-paused for high bounces again for 7 days. | 10 Nov 2026 |
| Smartlead | High Bounce Rate Auto Protection pauses a campaign when it reaches a threshold you set in campaign setup. The page gives 5% and 3% as examples and states no default. | 10 Nov 2026 |
| lemlist | Bounce rate alerts trigger at 10%. Campaigns pause automatically at 50% once at least 100 leads have been contacted. | 10 Nov 2026 |
These are product safety nets set well above the 2% guidance, and they act on a campaign, while the guidance is per mailbox. lemlist shows the gap: its blog advises stopping above 15%, and its help center pauses at 50%. Plan to the guidance, not to the pause line.
Why do cold lists bounce more than opt-in lists?
Nobody on a cold list confirmed the address. lemlist puts it this way: "Pattern guessing without verification creates addresses that look plausible but don't exist."
People change jobs. The U.S. Bureau of Labor Statistics reported median tenure of 4.1 years in January 2026, and 3.0 years for workers aged 25 to 34 (released 24 Sep 2026). Tenure is a proxy for job changes, not an email-decay figure.
Lists decay after a check. In Hunter's 8-week test, published 4 Nov 2025, 2.3% of previously verified addresses (29 of 1,278) became invalid and 3.2% became accept-all.
Catch-all domains accept mail at the door and can bounce it later. Trueguard's advanced catch-all detection validates the mailbox where it can and returns safe with isCatchall: true. An address it cannot validate comes back risky.
How many bounces does an unverified list cost?
The example assumes a hypothetical list of 5,000 contacts where 6% of addresses are invalid. 6% is an example, not a measured average.
| Sent | Hard bounces | Bounce rate | Against 2% guidance | Against 5% (SES review, Instantly pause) | |
|---|---|---|---|---|---|
| Unverified whole list | 5,000 | 300 | 6.0% | 3 times over | Over |
| First 200 sends of one campaign | 200 | 12 | 6.0% | Over | Instantly pauses (over 5% after 200 sends) |
| Verified, invalid dropped | 4,700 or fewer | 0 known invalid | Depends on decay and catch-all |
Small volumes swing fast. At 100 sends, 2 bounces is 2% and 5 is 5%. Instantly's check starts at 200 sends, where 10 bounces is 5%, not yet above its line, and 11 trips it.
Start with a sample. The first 100 validations a month are free, no card: if 6 of 100 come back invalid, you have measured your own list. All 5,000 checks fit inside Standard, which is $49.99 a month for 50,000 validations (see the email verification API), and all 5,000 count, including the 300 invalid. 60,000 checks cost $49.99 + 10,000 × $0.001 = $59.99.
Dropping invalid addresses removes the bounces you can see in advance. Decay after the check and catch-alls that cannot be validated can still bounce, which is why risky and unknown are held.
What should you do if a mailbox goes over 5%?
- Pause the campaign, or let the sequencer do it.
- Stop sending to every bounced address. Amazon SES's guidance is to "remove bounced addresses from your mailing list and stop sending mail to them immediately."
- Verify the rest of the list before resuming.
- Resume at lower volume and ramp up slowly, as Gmail's guidance says. Keep SPF, DKIM and DMARC in place while you do.
- Check Delivery Errors and Domain Reputation in Google Postmaster Tools (personal Gmail recipients only), and compare bounce rate by list source to find the bad source.
No provider publishes a recovery time, so this page gives none.
What does the API response look like?
Send one address, get one result. Route on deliverability.status: send safe, hold risky and unknown, drop invalid.
const res = await fetch("https://api.trueguard.io/v2/email/validation", {
method: "POST",
headers: {
"X-API-KEY": process.env.TRUEGUARD_KEY,
"Content-Type": "application/json"
},
body: JSON.stringify({ email: "name@gmail.com" })
});
const result = await res.json();
console.log(result.deliverability.status); // "safe"{
"email": "name@gmail.com",
"rawEmail": "name@gmail.com",
"syntax": { "isValid": true },
"deliverability": {
"status": "safe",
"isSmtpValid": true,
"isMxValid": true,
"isCatchall": false,
"isInboxFull": false,
"isDeliverable": true,
"isDisabled": false,
"mxRecords": [
"gmail-smtp-in.l.google.com",
"alt1.gmail-smtp-in.l.google.com",
"alt2.gmail-smtp-in.l.google.com",
"alt3.gmail-smtp-in.l.google.com",
"alt4.gmail-smtp-in.l.google.com"
]
},
"domain": {
"name": "gmail.com",
"age": 11363,
"isLive": true,
"isRisky": false
},
"quality": {
"isDisposable": false,
"isFree": true,
"isRole": false,
"isSubaddress": false
}
}Frequently asked questions.
Still deciding? Contact support or read the API reference.
What is a good bounce rate for cold email?
Under 2% of emails sent, watched per sending mailbox. Amazon SES recommends staying below 2%, and no mailbox provider publishes a stricter number. The bounces you can prevent are addresses that do not exist: Trueguard's email verification API checks each address before it enters a sequence and returns safe, risky, invalid or unknown. 100 checks a month are free, no card.
Is a 5% bounce rate bad for cold email?
Yes. Amazon SES puts accounts under review at 5%, and Instantly's help center (read 10 Nov 2026) says it auto-pauses a campaign above 5% once the campaign has sent at least 200 emails. Stop the campaign, remove the bounced addresses, and verify the rest before you resume.
At what bounce rate do Gmail and Outlook flag you?
Neither publishes one. Gmail's sender guidelines set a spam-rate limit (under 0.10%, never 0.30%) and tell senders to reduce volume when messages bounce. Outlook.com lists removing invalid addresses as a recommendation. The 8% figure that circulates is a limit for Microsoft Dynamics 365 Customer Insights Journeys, not Outlook.com.
Do bounces hurt my domain reputation, and how long does recovery take?
Amazon SES says high bounce rates are used by email providers and anti-spam organizations to detect bad sending practices and can push mail to spam. Yahoo says invalid recipients harm reputation. No provider publishes a recovery time. Watch Domain Reputation in Google Postmaster Tools while you ramp back up.
Should I send to catch-all email addresses?
It depends on the result. Trueguard has advanced catch-all detection that can validate a mailbox on a catch-all domain. A validated address comes back safe with isCatchall: true, and you can send to it. An address that cannot be validated comes back risky with isCatchall: true: keep it out of the main campaign.
How often should I re-verify a cold list?
Before each campaign, if the list has waited weeks. In Hunter's 8-week test, 2.3% of previously verified addresses became invalid. Outlook.com recommends removing invalid addresses regularly, monthly or quarterly.
Can I upload a CSV of my cold list?
No. Trueguard has no bulk upload and no sequencer app. A short script calls the API once per address and writes send, hold and drop files. Deduplicate first: every successful check is billed, including invalid results.
Can email verification guarantee zero bounces?
No. A check is a snapshot: addresses go bad after it, and catch-all domains that cannot be validated may accept mail and bounce later. Verification removes the addresses you can identify as bad before you send, which is why the API returns risky and unknown instead of forcing every address into valid or invalid.
Other use cases
Verify the list before the sequence sends.
100 validations a month, free, no card. Check 100 addresses from your next cold list and see how many would have bounced.
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