Bounce rate by list source: which import, vendor or segment caused the bounces?
In short: Reads a send or activity export (one row per recipient with a status column) and splits hard bounces, soft bounces, blocks, complaints and unsubscribes by any column (lead source, list, tag, campaign, import date) or by the recipient's mailbox provider. Flags groups at 2% hard bounces or 0.1% complaints; downloads the breakdown and the rows of flagged groups. Limit: It reads the statuses your platform recorded; rows it can't read count as sent and are reported.
Upload the export of the send that went wrong, with a status column and a column saying where each contact came from. The tool groups the rows by that column, or by Gmail, Outlook, Yahoo and company domains, and shows each group's hard bounce and complaint rate, flagging any at 2% bounces or 0.1% complaints so you know which source to verify or drop.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. See pricing
Sample result
Vendor list bounced 75%; the webinar list drew the complaint; the signup form is clean.
- Groups
- 3
- Worst
- Vendor list, 75%
- Rows to verify
- 8
What this means for you
Stop mailing the vendor list and verify it; the bounces came from one source, not the whole file.
- Group by any column
- Or by Gmail, Outlook, Yahoo
- Hard, soft, blocked, complaints
- Flagged rows to download
- Bounce rate
- Lead sources
- CSV
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
How do I clean the source that caused it?
- Download the rows from the flagged groups, not only the addresses that bounced.
- Upload them at /verify. Every address gets a live mailbox check, and valid, risky and invalid download as separate files. The first 100 email checks are free with a Google sign-in, no card.
- Keep the valid file, and ask the vendor or the import owner where the rest came from.
How do I find which list caused high bounces?
- Export the campaign's recipients from your ESP or sequencer with their status (delivered, bounced, complained) and a source, list, tag or campaign column. If the export has no source, join it from your CRM first.
- Paste it or upload the CSV and press Break down by source.
- Pick the column to group by, or the recipient's mailbox provider to see whether one provider is the problem.
- Download the rows from flagged groups, verify them, and stop mailing that source until it's clean.
Example
- You enter
- A 12-row send export with email, status and lead_source columns: 4 rows from a webinar (1 spam complaint), 4 from a vendor list (3 hard bounces) and 4 from the signup form (1 mailbox-full soft bounce).
- You get
- Grouped by lead_source: Vendor list 75% hard bounces (flagged), Webinar 25% complaints (flagged), Signup form under both lines but too few rows to judge. Overall 25% hard bounces; 8 rows from the flagged groups download for verification.
- Limits
- Runs in your browser with no row cap; an uploaded file can be up to 25 MB.
Why break bounces down by source?
Because a bounce spike almost always has one cause: an old import, one lead vendor, a scraped segment, a webinar list nobody cleaned. The overall rate says something went wrong; the per-source rate says what to stop mailing. A 3% campaign bounce rate can be 0.4% on your signup form and 14% on one purchased file.
Grouping by mailbox provider answers a different question. If Outlook.com addresses bounce or block and Gmail ones don't, the problem is your standing with Microsoft, not the list; Bounce Doctor reads the bounce codes to confirm it.
How is each row read?
From the status, event, type, bounce type, reason and code columns together. A 5.1.x or 5.2.x code, or words like hard bounce, user unknown or does not exist, is a hard bounce; a 4.x.x code or mailbox full, deferred or try again later is soft; 5.7.x and policy, blocklist or reputation wording is a block on the sender; complaint, spam report or FBL is a complaint. Bounce rate is hard bounces over rows in the group; complaint rate is complaints over rows that didn't bounce.
The flag lines are 2% hard bounces (Amazon SES's recommended maximum and Brevo's suspension line) and 0.1% complaints (Google's spam-rate target). A group under 50 rows that is under both lines is marked too few to judge rather than cleared, since one more bounce would move it a lot.
Who uses this tool, and for what?
- Marketing ops
- Find the import or form that caused a bounce spike before the next campaign.
- Cold emailers
- Compare lead vendors by the bounces their files produced, and stop paying for the worst one.
- Agencies
- Show a client which of their lists broke the campaign, with the numbers.
What can’t this tool tell you?
- It reads the statuses your platform recorded; rows it can't read count as sent and are reported.
- Mailbox provider grouping comes from the address only; company domains are one group, since their host needs a DNS lookup.
- Small groups swing hard: one bounce in 20 rows is 5%.
- It shows which source bounced, not which of its remaining addresses will. That needs a mailbox check.
Common questions
- My ESP export has no source column. What do I do?
- Join it from your CRM by email (the CSV merge tool does this), or group by a column the export does have, such as tag, list or import date.
- What bounce rate should a lead source have?
- Under 2% hard bounces is under every published ESP line. A source over that on a first send is usually old, bought or guessed.
- Does it check the addresses?
- No. It reads the results your platform already recorded. To check the addresses themselves, use /verify.
- Is my file uploaded?
- No. It's read in your browser.
Sources
Clean the list before the next send.
A bounce report only tells you about the addresses you already mailed. The rest of the list has the same kinds of dead mailboxes in it, and each one becomes a hard bounce recorded against your domain the moment you send.
- A real SMTP mailbox check on every row, before anything is sent
- Dead and mistyped addresses split out, so they never reach your sending tool
- Catch-all, disposable and role addresses flagged alongside
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.