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How to Connect a Mailbox in FirstSales

Connect a sending mailbox via Google, Microsoft, or SMTP/IMAP, authenticate the domain, and turn on warm-up before your first send.

Tutorials
Mailboxes
min read
7 min
steps
6 · Beginner

  1. Open Connectors and click Add Connector

    In FirstSales a sending mailbox is called a connector: "the mailboxes and integrations that send your campaigns." Open the Connectors page from the left nav and click Add Connector (top-right).

    Every campaign sends from a connector, so this is the first thing to set up before launching anything. You can add as many as you like.

    Open Connectors and click Add Connector

  2. Pick how you'll connect

    Choose one of three email account types:

    • Google (connect a Google Workspace account via OAuth (one click, no password stored).
    • Microsoft) connect a Microsoft/Outlook account via OAuth.
    • SMTP / IMAP (connect any other provider with server credentials.

    Important: for Google, only Google Workspace accounts are supported) personal @gmail.com addresses are not allowed. Use a domain mailbox (e.g. [email protected]).

  3. Connect with Google or Microsoft (OAuth)

    For Google or Microsoft, click the connect button and a popup opens to authorize FirstSales. Sign in and grant access; the window shows "Waiting for authorization…" and then confirms "{Provider} connected". FirstSales never sees or stores your password: it holds a revocable OAuth token.

    If your Google Workspace admin restricts third-party apps, they may need to allow FirstSales in the admin console first. If authorization fails, use Try again.

    Connect with Google or Microsoft (OAuth)

  4. Or connect via SMTP / IMAP

    For any other provider, choose SMTP / IMAP and the Single Account tab. Fill in:

    • Email address and optional Display name.
    • Username and Password.
    • Outgoing (SMTP): host, port (587 / 465 / 25 / 2525 or custom), encryption (TLS / SSL / None). Default 465 / SSL.
    • Incoming (IMAP): host, port (993 / 143), encryption. Default 993 / TLS.

    IMAP is included so FirstSales can read replies and route them to your inbox.

  5. Test the connection, then add the account

    For SMTP/IMAP you must click Test connection first. On success you'll see "Connection verified (ready to save," and only then can you click Add account) you can't save an untested mailbox. A toast confirms "Email account added!"

    This test catches wrong hosts, ports, or app-password issues up front, so a bad mailbox never silently fails mid-campaign.

  6. Warm it up before sending

    A brand-new mailbox has no sender reputation. Before you point real campaigns at it, open the connector's Warm Up tab and enable warm-up so it gradually builds reputation. See the email warm-up tutorial for the full setup.

    Connecting the mailbox is step one; warming it is what keeps your first real sends out of spam.

Pro tips

  • Use a Google Workspace account, not personal Gmail

    Personal @gmail.com addresses aren't supported: only Google Workspace (domain) accounts. Cold outreach should send from your own domain anyway, so this lines up with good practice.

  • OAuth beats SMTP when you have the choice

    Google and Microsoft OAuth store a revocable token, not your password, and reconnect cleanly if access lapses. Reach for SMTP/IMAP only when your provider isn't one of those two.

  • A failed test now saves a dead campaign later

    The SMTP 'Test connection' gate exists so a wrong port or password surfaces immediately. Don't work around it: fix the credentials until the test passes.

  • Connect, then warm up

    A freshly connected mailbox has zero reputation. Turn on warm-up right after connecting so it's ready by the time you launch real outreach.

Frequently asked questions

What is a 'connector'?

It's FirstSales' name for a sending mailbox (or integration): the account your campaigns send from. You manage them on the Connectors page and add one with Add Connector.

Which mailbox types can I connect?

Three: Google (Workspace, via OAuth), Microsoft/Outlook (via OAuth), and SMTP / IMAP for any other provider using server credentials.

Can I use a personal Gmail account?

No. Only Google Workspace accounts are supported for Google: personal @gmail.com addresses are blocked. Connect a mailbox on your own sending domain instead.

Does FirstSales store my password?

For Google and Microsoft, no: it uses OAuth and holds a revocable token. For SMTP/IMAP you provide credentials directly so it can send and read replies; use an app password where your provider offers one.

Why do I need IMAP settings too?

IMAP lets FirstSales read incoming mail so replies to your campaigns land in your FirstSales inbox and can end a contact's sequence. That's why the SMTP/IMAP form asks for both outgoing and incoming servers.

Why can't I click 'Add account' yet?

For SMTP/IMAP you must run Test connection first. Until it verifies ('Connection verified (ready to save'), the save button stays disabled) this prevents adding a mailbox that can't actually send.

What if OAuth authorization fails?

Use Try again. If it keeps failing on Google Workspace, your admin may need to allow FirstSales in the Google admin console. For an existing connector that lost access, use Reconnect account on the connector card.

What should I do right after connecting?

Enable warm-up on the connector's Warm Up tab. A new mailbox has no reputation, and warming it first is what keeps your early sends landing in the inbox.

Mailboxes

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Install with AI

Your coding agent sets up the FirstSales CLI and skills for you.

Prompt for Claude Code

I'm setting up FirstSales (https://firstsales.io), an AI outbound sales platform: campaigns, contacts, a reply inbox, deliverability and lead signals. Help me get my workspace sending real, good emails end to end, from Claude Code.

Read these first so you know how FirstSales works:
- Developer docs and API: https://developer.firstsales.io
- CLI: https://www.npmjs.com/package/@firstsales.io/cli
- Skills for coding agents: https://github.com/firstsalesio/firstsales-skills (read README.md and GUIDE.md)

Setup
1. Install the CLI: npm install -g @firstsales.io/cli
2. Install the FirstSales skills:
   claude plugin marketplace add firstsalesio/firstsales-skills
   claude plugin install firstsales@firstsales
3. Ask me if I already have a FirstSales account. If not, send me to https://app.firstsales.io to sign up.
4. Ask me to create an API key under Settings → API → API Keys, with only the scopes we need.
   Never ask me to paste the key into this chat. Tell me to run this in my own terminal, so the key stays hidden:
   read -rs FS_KEY && firstsales auth login --api-key "$FS_KEY"; unset FS_KEY
5. Run `firstsales whoami` and tell me which workspace and organisation we are connected to.

Then ask me about my business: what I sell, who I sell to (roles, company size, countries), my best customers, and what I use today for outbound (tools, lists, mailboxes). Walk me through:
1. Teaching FirstSales my business: website, offer, proof points and case studies in the knowledge base, so the AI writes like someone who knows the product.
2. Connecting my sending mailboxes and checking my sending domain: SPF, DKIM, DMARC and warm-up. If anything is unhealthy, tell me the exact DNS record to add.
3. Bringing in contacts: import my CSV or CRM export into a clean list, remove duplicates and bad emails, and block domains I must never email (customers, competitors, my own).
4. Building my first campaign: the right list, senders, steps and timing. Write the sequence with me, show me the drafts, and do not launch until I say yes.
5. Setting up Signals if it fits: find people engaging with LinkedIn posts about topics my buyers care about, and turn them into leads.
6. Inviting my team and giving each person the right access.

Once campaigns run, show me how to work the reply inbox from here: which replies need an answer, draft responses in my voice, and move good conversations into deals. If I use Cal.com, connect it so follow-ups can offer my booking link (not the first email).

Throughout, as you learn about my business, proactively suggest and help create:
- Reply templates for the questions and objections my prospects are likely to raise, based on my product, site and codebase if you can see them.
- Campaign ideas and segments worth testing, with the reason for each.

Safety rules:
- Show every change as a dry run (--dry-run) first and wait for my yes. Never send emails, launch campaigns or delete anything without my yes.
- Tell me before anything that spends credits, and how many.

Be opinionated. If the docs give a sensible default, just use it. Don't make me choose between five options.
Developer docs ↗npm: @firstsales.io/cli ↗GitHub: firstsales-skills ↗