---
title: "Bulk-add mailboxes via CSV | FirstSales"
description: "Upload a CSV to add many SMTP/IMAP mailboxes at once, with column mapping and per-row validation before import."
canonical: "https://firstsales.io/tutorial/bulk-import-smtp-mailboxes/"
---

[Home](/)/[Tutorials](/tutorial/)/Bulk-add mailboxes via CSV

Mailboxes

# Bulk-add mailboxes via CSV

Upload a CSV to add many SMTP/IMAP mailboxes at once, with column mapping and per-row validation before import.

6 min read·Intermediate·8 steps

1. 1  
## Connectors → Add Connector → SMTP/IMAP → Bulk Upload (CSV)  
Open the **SMTP / IMAP** connector and switch to the **Bulk Upload (CSV)** tab — the second tab next to Single Account.
2. 2  
## Download the sample CSV  
Click **Download sample CSV** (`sample-mailboxes.csv`) and fill your mailboxes into its columns. It's the exact schema the importer expects, so its headers auto-map without extra work.
3. 3  
## Know the required columns  
Every row needs **Email**, **SMTP Username**, **SMTP Password**, **SMTP Host**, and **IMAP Host**. Everything else — ports, encryption, Daily Limit, warm-up columns — is optional and defaults sensibly.  
   * Full column set: Email, First Name, Last Name, IMAP Username, IMAP Password, IMAP Host, IMAP Port, SMTP Username, SMTP Password, SMTP Host, SMTP Port, Daily Limit, Warmup Enabled, Warmup Limit, Warmup Increment.
4. 4  
## Upload the file  
Drag your `.csv` onto the dropzone or click to select it. Files are limited to **5MB** and **up to 5,000 rows**. FirstSales parses it and moves straight to the preview.  
![Upload the file](/tutorials/bulk-mailboxes-01-upload.webp)
5. 5  
## Check the column mapping  
Columns auto-map by header name. Use each column's **→** dropdown to fix any that didn't match, or set it to **\- Skip -**. Required fields are marked with `*` — an amber warning appears if any required column is unmapped.  
![Check the column mapping](/tutorials/bulk-mailboxes-02-mapping.webp)
6. 6  
## Review the validation preview  
The first 5 rows show a green check or an amber warning, plus a **Total / Valid / Invalid** summary. Validation checks email format, host fields, credentials, port ranges (1–65535), and **Daily Limit** (1–10000). Invalid rows are skipped on import — fix them in your CSV and re-upload if you want them all in.
7. 7  
## Click Import  
Click **Import N valid accounts**. A progress bar runs as each mailbox is added one at a time.
8. 8  
## Read the results  
The done screen shows **Imported** and **Failed** counts, with a failed-rows list and reasons. Use **Import More** for another batch, or **Done** to finish — then warm up the new mailboxes before real sends.

## Pro tips

Hard-won shortcuts that keep warm-up on track.

1

### Start from the sample CSV

Its headers map automatically. Renaming your columns to match (“SMTP Host”, “IMAP Host”, …) saves you re-mapping every field by hand.

2

### Fix invalid rows before importing, not after

The preview flags bad emails, hosts, and out-of-range ports up front. Invalid rows are silently skipped, so a clean CSV means nothing goes missing.

3

### Set warm-up columns per row

Warmup Enabled, Warmup Limit, and Warmup Increment let you enable ramp-up at import time instead of toggling each mailbox afterward.

4

### Batch large lists

5,000 rows is the ceiling per file. For bigger fleets, split into files and use Import More between batches.

## Frequently asked questions

Where's the bulk importer?

On the SMTP/IMAP connector: **Connectors → Add Connector → SMTP / IMAP → Bulk Upload (CSV)**.

What columns do I need?

Required: **Email**, **SMTP Username**, **SMTP Password**, **SMTP Host**, **IMAP Host**. Optional: ports, encryption (inferred from port), **Daily Limit**, and the three Warmup columns.

What are the limits?

A CSV under **5MB** and up to **5,000 rows** per file.

My columns didn't map — what do I do?

Use the per-column **→** dropdown in the preview to map each header to the right field, or set it to **\- Skip -**.

What happens to invalid rows?

They're flagged in the preview and skipped on import; the done screen lists each failure and its reason.

What defaults apply if I omit a column?

SMTP port `587`, IMAP port `993`, encryption inferred from the port, **Daily Limit 30**, warm-up off, warm-up limit 20, warm-up increment 2.

Can I import more than one file?

Yes — after a batch finishes, click **Import More** to run another.

Do bulk-imported mailboxes get warmed up?

Only if you set the **Warmup** columns, or enable warm-up per mailbox afterward. Reputation still has to build before real sends.

## Ready to put this into practice?

Start your FirstSales trial and launch a warmed, authenticated mailbox in minutes.

[Start for $1](https://app.firstsales.io)

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