Lead to inbox assigner: split a lead list across your sending inboxes
In short: Upload a lead list and paste your inbox addresses. Every lead gets a Sender inbox column, the inboxes carry an even share, an optional cap stops any one inbox taking too many, and leads at one company stay together or are spread out, as you choose. Limit: The cap counts leads for the whole file, not emails per day.
Upload your lead list, paste the inbox addresses you send from, and the tool adds a Sender inbox column that gives each inbox an even share. You choose whether leads at the same company stay on one inbox or go to different ones, and you can cap how many leads one inbox takes. Download the file and load each inbox's rows into its campaign.
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
Leave empty for an even split with no cap.
Sample result
Seven leads and three inboxes: the two leads at example.com share one inbox, and the inboxes carry 3, 2 and 2 leads.
- Leads assigned
- 7 leads
- Inboxes
- 3
- Same company
- Kept together
What this means for you
Every row gets a Sender inbox, so you can load each inbox's share into its own campaign.
- Even share per inbox
- Optional cap per inbox
- Companies together or spread
- CSV with Sender inbox
- Cold email
- Inboxes
- CSV
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
Each inbox should only get addresses that exist.
- Copy the Email column from the file you just made, or use the check button under the result.
- 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 divide cold email leads between inboxes?
- Upload the lead list (.xlsx or CSV), or paste the cells with the header row first. The email column is found for you.
- Paste your sending inboxes, one per line, and choose whether leads at the same company stay together or are spread across inboxes.
- Set a cap per inbox if you have one, then read the table of leads per inbox. Rows over the cap are counted and left unassigned.
- Download the CSV, split it by the Sender inbox column and load each part into the campaign for that inbox.
Example
- You enter
- Seven leads with Name, Email and Company: two at
example.com, one atexample.org, two atexample.net, and one each atexample.ioandexample.co; three inboxes,sender1@example-outreach.comtosender3@example-outreach.com; leads at one company kept together; no cap. - You get
- A Sender inbox column on every row: the two
example.comleads share one inbox, the twoexample.netleads share another, and the inboxes carry 3, 2 and 2 leads. No company is split across inboxes. - Limits
- Runs in your browser; nothing is uploaded. Files up to 25 MB.
How are leads divided between inboxes?
Every inbox is given the same number of leads, give or take one. In keep-together mode, companies are placed largest first, each onto the inbox with the lightest load that can take all of it, so one company is contacted from one address. In spread mode, each lead goes to the lightest inbox that has not yet been given a lead at that company, so the company hears from different addresses. Addresses at Gmail, Outlook and other personal mailboxes are never treated as one company.
What should the cap per inbox be?
That is your number: it depends on how many emails each inbox sends a day, how long the campaign runs and what your provider allows. Providers publish their own limits, for example Google Workspace and Exchange Online. This tool caps leads per inbox for the whole file, not per day; to spread leads over days as well, use the send schedule planner.
Why check the list before it is split?
A dead address bounces from whichever inbox it was given, so one bad block of rows can hurt a single inbox's record. Checking the list first keeps the bounces out of every inbox. See inbox rotation for what rotating inboxes does and does not spread.
Who uses this tool, and for what?
- Cold email agencies
- Give each client mailbox its own block of a shared list without hand-sorting a spreadsheet.
- SDR managers
- Divide a purchased or exported list across the team's sending addresses before the campaign starts.
- Founders
- Load a first list across two or three inboxes with the same share on each.
What can’t this tool tell you?
- The cap counts leads for the whole file, not emails per day.
- It does not know which inboxes are warm or which are on which provider; give it only the inboxes that should send.
- Equal shares are not always the right shares; an inbox with more warm-up history may deserve more.
- Company is judged by the email domain, so two domains of one company count as two.
Common questions
- Does this send anything or connect to my inboxes?
- No. It only adds a column to your file, and your inbox addresses are used as labels.
- Should leads at one company go to the same inbox?
- That is your choice, so the tool offers both. Keeping a company on one inbox means one sender per company; spreading means several of your addresses contact it.
- What happens to rows over the cap?
- They get no inbox, are counted in the results, and stay in the file with an empty Sender inbox so you can add inboxes and run it again.
- Are free-mail addresses grouped by domain?
- No. Two people at gmail.com are not at one company, so each personal address counts as its own company.
- Is my lead list uploaded to SimpleVerifier?
- No. The file is read and rewritten 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.