Bounce domain hotspot finder: which company domains are bouncing your emails?
In short: Upload a send or activity export with an email column and a status column. Each company domain shows how many addresses you sent to and how many bounced, and the domains where bounces cluster are flagged with the addresses still worth checking. Limit: It trusts the status column; a wrong or missing status gives wrong counts.
Upload a send or activity export with an email column and a status column. The tool groups the addresses by company domain and shows, for each, how many you sent to, how many bounced and the rate, then flags domains where bounces cluster, such as every address bouncing. It also lists the addresses at those domains that have not bounced yet, to check before the next send.
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. Check your list free nowSee pricing
Matched anywhere in the cell, any case.
Percent of the addresses sent to that domain.
Sample result
example.io is flagged because both addresses bounced, and example.com because 3 of 4 did.
- Domains flagged
- 2 domains
- Addresses
- 12
- Bounced
- 7
What this means for you
The bounces sit on a few company domains, so check the addresses still on them before the next send.
- Sent, bounced and rate per domain
- Hotspot rule you set
- Personal mailboxes kept apart
- Addresses left to check
- Bounces
- Domains
- CSV
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
The rest of a hotspot domain may be just as dead.
- Use the check button under the result to send the addresses at flagged domains that have not bounced.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I find which domains are causing my bounces?
- Export the send or lead activity from your sequencer or email platform, with the address and the status of each row.
- Upload it (.xlsx or CSV) or paste the cells, and set the status text that marks a bounce if yours isn't the word bounce.
- Read the flagged domains, set the bounce count and share that make a domain a hotspot, and download the table.
- Check the addresses that have not bounced at flagged domains before you email them again.
Example
- You enter
- A send export of 12 addresses with Email and Status: three of four addresses at
example.commarked Bounced, one of three atexample.net, none of two atexample.org, two of two atexample.io, and one Gmail address marked Bounced. Bounce text:bounce; flag at 2 bounced and 50%. - You get
example.iois flagged because every address bounced, andexample.combecause 3 of 4 did.example.nethas one bounce and is listed without a flag. The Gmail address is counted with personal mailboxes and not grouped. The oneexample.comaddress that did not bounce is offered for checking.- Limits
- Runs in your browser; nothing is uploaded. Files up to 25 MB.
What counts as a hotspot?
A domain is flagged when at least your chosen number of its addresses bounced and the bounced share is at least your chosen percent. A domain where every address bounced, with two or more sent, is flagged on its own. Domains with a couple of bounces below that are marked to watch. Personal mailboxes such as Gmail and Outlook are counted together and never flagged, because each bounce there is one person's mailbox, not a company's mail setup.
Why do bounces cluster on one domain?
Common causes are a company that closed or moved its mail, a naming pattern that was guessed wrong for every employee, a mail server that rejects your sending address, or a list built from one outdated source. The text of the bounce tells them apart: see enhanced status codes and RFC 3463. An every-address bounce does not prove the domain is dead; read a few bounce messages before you drop it.
What should I do with the other addresses at a hotspot?
Do not send to them again until they have been checked. Mail servers can accept a message and report the failure afterwards, as described in RFC 5321, so a quiet address at a bad domain is not proof that it works. See bounces from one domain for the next steps.
Who uses this tool, and for what?
- Cold emailers
- Find the one or two company domains behind a bounce spike and pull the rest of their addresses.
- Deliverability consultants
- Show a client which recipient domains hold their bounces.
- Sales ops
- Spot a bad data source by the domains it filled.
What can’t this tool tell you?
- It trusts the status column; a wrong or missing status gives wrong counts.
- It can't tell a closed domain from one that rejects your sender; the bounce message does.
- Domains are matched as written, so a company with several domains shows as several.
- Soft and hard bounces count the same unless your status text tells them apart.
Common questions
- What does the export need to contain?
- An email column and a column with each row's status. Any status text that contains your bounce word counts, in any case.
- Why are Gmail and Outlook addresses not flagged?
- They are shared by millions of people, so a bounce there says nothing about other addresses at the domain.
- Does it matter if an address appears twice?
- Repeats are merged; an address counts as bounced if any of its rows is a bounce.
- Is this a bounce rate calculator?
- It shows the rate per domain. For the overall rate or the rate by source, use the bounce rate calculator or the bounce rate by source tool.
- Is my export uploaded to SimpleVerifier?
- No. The file is read in your browser.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
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.