Bulk mailbox CSV for Google Workspace and Microsoft 365 sending domains
In short: Takes your sending domains, the sender names and the address formats you want (jane@, jane.doe@…), and writes one row per mailbox in the CSV format each admin console's bulk upload takes, with random passwords for Google made in your browser. Limit: It writes the CSV only; it can't check that a domain is added to your account or that you have licences.
To create many inboxes at once, list your sending domains and sender names, pick address formats such as jane@ and jane.doe@, and set mailboxes per domain. You get the Google Workspace bulk upload CSV (with the five required columns and random passwords) and the Microsoft 365 add-multiple-users CSV, ready to upload in each admin console.
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
Up to 200. Domains you have already bought and added to the admin console.
Real people on your team who will answer the replies. Accents are folded for the address.
1 to 10.
/ is the top-level organisational unit.
Sample result
3 domains x 2 senders became 9 mailboxes, ready for the Google Workspace bulk upload.
- Mailboxes
- 9
- Domains
- 3
- Formats
- jane@, jane.doe@
What this means for you
Upload the CSV in your admin console, then delete it: it holds the passwords.
- Domains x names x formats
- Google's five required columns
- Microsoft's exact headings
- Random passwords, in your browser
- Inboxes
- Admin console
- CSV
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
How do I create cold email inboxes in bulk?
- List the sending domains you've bought and added to your Google Workspace or Microsoft 365 account, one per line.
- List the sender names, one per line, and pick the address formats in the order you want them used.
- Set mailboxes per domain and press Build the mailbox CSV.
- Download the Google Workspace or Microsoft 365 file and upload it in the admin console, then delete the file: the Google one holds passwords.
Example
- You enter
- 3 sending domains (
getnorthwind.example,trynorthwind.example,northwindhq.example), 2 senders (Jane Doe, Sam Lee), formats first@ then first.last@, 3 mailboxes per domain. - You get
- 9 mailboxes:
jane@,sam@andjane.doe@on each domain. The Google Workspace CSV has the five [Required] columns with a random 16-character password per row and org unit/; the Microsoft 365 CSV has its 16 headings with user name and display name filled. - Limits
- Up to 200 domains, 50 sender names and 10 mailboxes per domain a run; passwords are made in your browser.
How do I bulk create users in Google Workspace with a CSV?
In the Google Admin console, go to Directory, Users, then Bulk update users, and upload a CSV. Google's help lists five required columns, First Name [Required], Last Name [Required], Email Address [Required], Password [Required] and Org Unit Path [Required], says optional columns can be left out, and that / puts users in the top-level organisational unit. A file can hold up to 150,000 records (Google: Add or update multiple users from a CSV file).
Passwords must have at least 8 characters by default, and your organisation can require more. The passwords made here are 16 characters with upper and lower case, digits and symbols, generated with your browser's cryptographic random number generator.
How do I add multiple users in Microsoft 365?
In the Microsoft 365 admin center, go to Users, Active users, then Add multiple users, and upload a CSV with exactly the same column headings as Microsoft's sample: User Name, First Name, Last Name, Display Name and twelve more. Microsoft requires a user name (the address) and a display name for each user (Microsoft: Add several users at the same time).
The Microsoft file here has every heading in order with those columns filled; Microsoft creates the passwords and shows them when the import finishes, and you choose the licence for all of them in the same flow.
How many inboxes per domain for cold email?
Commonly two or three, each sending a modest daily volume, with more domains rather than more inboxes per domain; our guides to how many domains for cold email and secondary domains explain the trade-offs, and the cold email volume calculator works out the numbers for a daily target.
Use real names of people who will read the replies. Every new domain also needs SPF, DKIM and DMARC before the first send; check them in bulk once the records are in.
Is this faster than filling in the template?
| This tool | Admin console template | |
|---|---|---|
| Domains x names x formats | Generated | Typed row by row |
| Random passwords | 16 characters, in the browser | Typed or made elsewhere |
| Google and Microsoft formats | Both | One template each |
| Duplicate addresses | Skipped | Upload error |
Who uses this tool, and for what?
- Cold emailers
- Set up 3 inboxes on each of 10 new sending domains in one upload instead of 30 forms.
- Agencies
- Build the same sender personas across a client's new domains, in the client's Google or Microsoft format.
- Founders
- Add first@ and first.last@ for two or three teammates on a new outreach domain.
- IT admins
- Generate a starter CSV with strong random passwords for a batch of new users on one domain.
What can’t this tool tell you?
- It writes the CSV only; it can't check that a domain is added to your account or that you have licences.
- Google's column names are the required ones from Google's help, checked 2 November 2026; if an upload is rejected, compare with the template in your admin console.
- Addresses are made from ASCII letters and digits; accents are folded and other characters dropped.
- Each mailbox is a paid licence in both Google Workspace and Microsoft 365.
Common questions
- What columns does the Google Workspace user CSV need?
- First Name [Required], Last Name [Required], Email Address [Required], Password [Required] and Org Unit Path [Required]. Optional columns can be left out.
- Can I add users on several domains in one file?
- Yes, as long as every domain is already added to the account (as a secondary domain in Google Workspace, or a verified domain in Microsoft 365).
- Are the passwords sent anywhere?
- No. They're made in your browser with crypto.getRandomValues and only exist in the file you download.
- What if a sender has no last name?
- Only the first@ format works for them; Google's file repeats the first name in the required Last Name column.
- Does this create the mailboxes?
- No. It writes the CSV; you upload it in the admin console, which creates the users and charges for their licences.
Sources
Authentication and capacity are half of deliverability.
The other half is who you send to. Every hard bounce counts against the domain and inboxes you are sending from, and nothing in DNS can tell you which addresses on your list are dead.
- Bulk verification with real SMTP mailbox checks
- Hard bounces removed before a send, not discovered after
- Catch-all, disposable and role detection on every row
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.