Connect a mailbox

5 min readconnect-mailbox

Link your Gmail, Outlook, or any SMTP provider to send cold emails.

Before you can send cold emails, connect at least one mailbox at /inbox/connect.

Option 1: Connect with Google (one-click OAuth)

If your admin has configured Google OAuth, you'll see a Continue with Google button.

Click it
Grant the gmail.send + gmail.readonly scopes
You're done — the mailbox is connected and ready to send

What Google sees: we never ask for "read all your email" or "access your contacts". Only the minimum scopes needed to send on your behalf and poll for replies.

Option 2: Manual SMTP / IMAP

Works with any provider. FlowMaticX ships with presets for:

Gmail / Google Workspace (with App Password)
Microsoft 365 / Outlook
Zoho Mail
Fastmail
Yahoo Mail
Resend
SendGrid
Mailgun
Postmark
Custom (any host you control)

Pick a preset from the dropdown and the SMTP host, port, and TLS settings auto-fill.

Gmail App Password (required for manual connect)

Gmail doesn't let you use your real password for SMTP. You need an App Password:

Enable 2FA on your Google account at myaccount.google.com/security
Go to myaccount.google.com/apppasswords
Pick "Mail" + your device → Generate
Copy the 16-character password (spaces allowed, spaces are stripped server-side)
Paste into the FlowMaticX SMTP password field

Signature (recommended)

Every outbound email gets the signature you set here auto-appended to the body. Keep it short:

Best, Your Name Founder · Your Company yourcompany.com

If you leave the signature blank, no footer is added.

Daily send limit

Protects your sender reputation. 200/day is the FlowMaticX default, which is safe for most providers. Providers like Gmail enforce a hard ceiling around 500/day for personal accounts and 2000/day for Workspace — stay comfortably under.

Warm-up mode (strongly recommended for new mailboxes)

New domains and mailboxes need to earn sender reputation slowly. Enable warm-up mode and set an hourly limit:

Week 1: 10/hour, ~80/day
Week 2: 30/hour, ~200/day
Week 3: 60/hour, ~300/day
Week 4+: disable warm-up, use daily limit only

The warm-up gate enforces the hourly ceiling on top of the daily limit. When the hour resets (every 60 min), the counter drops to zero.

Reply-to override

If you want replies to land in a different mailbox than the one you sent from, set a Reply-To address. Example: send from hello@yourcompany.com but have replies go to sales@yourcompany.com.

Managing multiple mailboxes

Connect as many mailboxes as you like. Each runs its own daily/hourly counters. When you send from a lead or a sequence, you pick which mailbox fires the email. For high-volume campaigns, split sends across multiple inboxes to stay under per-mailbox limits.

What if connection fails

"Authentication failed" — wrong password or App Password. Regenerate and retry.
"Connection timeout" — firewall blocking the port. For SMTP, check 587/465. For IMAP, check 993.
"Relay denied" — your provider needs you to use the exact From address, not a different one
Still stuck — check docs/EMAIL_TESTING.md for the admin diagnostic steps