Mailbox Setup

zend.sh is a BYOK (Bring Your Own Keys) platform. You connect your own mailboxes, and zend.sh handles rotation, health monitoring, and deliverability. This guide covers connecting the three supported provider types.

Google Workspace

Prerequisites

• A Google Workspace account (not a free @gmail.com account)
• 2-Step Verification enabled on the account

Generate an app password

1. Go to Google Account Security
2. Under "2-Step Verification", click App passwords
3. Select "Mail" as the app and your device
4. Copy the 16-character app password

Connect the mailbox

const account = await zend.accounts.create({
  email: 'outreach@yourcompany.com',
  provider: 'google',
  smtp_host: 'smtp.gmail.com',
  smtp_port: 465,
  smtp_username: 'outreach@yourcompany.com',
  smtp_password: 'xxxx xxxx xxxx xxxx', // app password
  imap_host: 'imap.gmail.com',
  imap_port: 993,
  imap_username: 'outreach@yourcompany.com',
  imap_password: 'xxxx xxxx xxxx xxxx', // same app password
})

Enable IMAP

IMAP must be enabled for reply detection:

1. Open Gmail settings (gear icon)
2. Go to Forwarding and POP/IMAP
3. Under IMAP Access, select Enable IMAP
4. Save changes

Microsoft 365

Microsoft 365 uses OAuth2 for authentication. You need to register an Azure AD application.

Register an Azure AD app

1. Go to Azure Portal > App registrations
2. Click New registration
3. Set a name (e.g., "zend.sh") and register
4. Under API permissions, add:
   • SMTP.Send (for sending)
   • IMAP.AccessAsUser.All (for reply detection)
5. Under Certificates & secrets, create a client secret

Connect the mailbox

const account = await zend.accounts.create({
  email: 'outreach@yourcompany.com',
  provider: 'microsoft',
  smtp_host: 'smtp.office365.com',
  smtp_port: 587,
  smtp_username: 'outreach@yourcompany.com',
  smtp_password: 'your-password-or-token',
  imap_host: 'outlook.office365.com',
  imap_port: 993,
  imap_username: 'outreach@yourcompany.com',
  imap_password: 'your-password-or-token',
})

Custom SMTP/IMAP

Any email provider that supports SMTP and IMAP can be connected: Zoho, Namecheap, Fastmail, self-hosted, etc.

const account = await zend.accounts.create({
  email: 'outreach@yourcompany.com',
  provider: 'smtp',
  smtp_host: 'smtp.yourdomain.com',
  smtp_port: 465, // or 587 for STARTTLS
  smtp_username: 'outreach@yourcompany.com',
  smtp_password: 'your-password',
  imap_host: 'imap.yourdomain.com',
  imap_port: 993,
  imap_username: 'outreach@yourcompany.com',
  imap_password: 'your-password',
})

Common provider settings:

Validate DNS records

After connecting a mailbox, validate SPF, DKIM, and DMARC records:

const result = await zend.accounts.test(account.id)
console.log(result)
// { success: true, message: 'Test email sent' }

Ensure your domain has proper DNS records:

• SPF — Authorizes your mail server to send on behalf of your domain
• DKIM — Digitally signs outgoing emails for authenticity
• DMARC — Tells receiving servers how to handle unauthenticated email

Best practices

1. Start with 2-3 accounts — Add more mailboxes as health scores stabilize above 80
2. Use dedicated sending domains — Avoid using your primary business domain for cold outreach
3. Set realistic daily limits — Start with 20-30 emails per account per day, increase gradually
4. Monitor health scores — zend.sh auto-pauses accounts when bounce rates exceed 2% or spam complaints exceed 0.3%
5. Warm up new accounts — Send small volumes to engaged contacts before scaling up cold outreach