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Provider Configuration

Each email provider has specific SMTP and IMAP settings. This guide covers the configuration for supported providers.

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Google Workspace

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Configuration

SettingValue
inbox_typeGOOGLE_WORKSPACE
smtp_hostsmtp.gmail.com
smtp_port587
smtp_use_tlstrue
imap_hostimap.gmail.com
imap_port993
imap_use_ssltrue
Max daily limit2,000

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App Password Setup

Google requires app-specific passwords when 2FA is enabled:
  1. Go to Google Account Settings
  2. Navigate to Security > 2-Step Verification
  3. Scroll to “App passwords”
  4. Generate a new app password for “Mail”
  5. Use the generated password in smtp_password and imap_password

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Example Request

requests.post(
    f"{base_url}/api/public/v1/sender-accounts",
    headers={"X-API-Key": api_key},
    json={
        "email_address": "[email protected]",
        "display_name": "John Smith from Company",
        "inbox_type": "GOOGLE_WORKSPACE",
        "daily_limit": 50,
        "smtp_host": "smtp.gmail.com",
        "smtp_port": 587,
        "smtp_username": "[email protected]",
        "smtp_password": "your-app-password",
        "smtp_use_tls": True,
        "imap_host": "imap.gmail.com",
        "imap_port": 993,
        "imap_username": "[email protected]",
        "imap_password": "your-app-password",
        "imap_use_ssl": True
    }
)

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Microsoft 365

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Configuration

SettingValue
inbox_typeOUTLOOK_365
smtp_hostsmtp.office365.com
smtp_port587
smtp_use_tlstrue
imap_hostoutlook.office365.com
imap_port993
imap_use_ssltrue
Max daily limit10,000

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App Password Setup

For Microsoft 365 accounts with modern authentication:
  1. Go to Microsoft Account Security
  2. Navigate to Advanced security options
  3. Find “App passwords” section
  4. Create a new app password
  5. Use the generated password in your configuration
Some Microsoft 365 tenants may not require app passwords if SMTP authentication is enabled. Check your organization’s security policies.

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Example Request

requests.post(
    f"{base_url}/api/public/v1/sender-accounts",
    headers={"X-API-Key": api_key},
    json={
        "email_address": "[email protected]",
        "display_name": "Sales Team at Company",
        "inbox_type": "OUTLOOK_365",
        "daily_limit": 75,
        "smtp_host": "smtp.office365.com",
        "smtp_port": 587,
        "smtp_username": "[email protected]",
        "smtp_password": "your-app-password",
        "smtp_use_tls": True,
        "imap_host": "outlook.office365.com",
        "imap_port": 993,
        "imap_username": "[email protected]",
        "imap_password": "your-app-password",
        "imap_use_ssl": True
    }
)

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Custom SMTP

Use custom SMTP for any email provider not listed above.

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Configuration

SettingDescription
inbox_typeCUSTOM_SMTP
smtp_hostYour SMTP server hostname
smtp_portYour SMTP port (typically 587 or 465)
smtp_use_tlsEnable TLS (recommended)
imap_hostYour IMAP server hostname
imap_portYour IMAP port (typically 993)
imap_use_sslEnable SSL (recommended)
Max daily limit100,000

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Common Ports

PortProtocolUse Case
587SMTP + STARTTLSRecommended for most providers
465SMTP + SSLLegacy, but still common
25SMTPOften blocked by ISPs
993IMAP + SSLStandard IMAP port

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Example Request

requests.post(
    f"{base_url}/api/public/v1/sender-accounts",
    headers={"X-API-Key": api_key},
    json={
        "email_address": "[email protected]",
        "display_name": "Outreach Team",
        "inbox_type": "CUSTOM_SMTP",
        "daily_limit": 100,
        "smtp_host": "mail.mydomain.com",
        "smtp_port": 587,
        "smtp_username": "[email protected]",
        "smtp_password": "your-password",
        "smtp_use_tls": True,
        "imap_host": "mail.mydomain.com",
        "imap_port": 993,
        "imap_username": "[email protected]",
        "imap_password": "your-password",
        "imap_use_ssl": True
    }
)

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Connection Validation

ColdSend validates both SMTP and IMAP connections before activating an account:

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SMTP Validation

  1. Connect to the SMTP server
  2. Send EHLO command
  3. Start TLS if enabled
  4. Authenticate with credentials
  5. Verify login succeeds

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IMAP Validation

  1. Connect to the IMAP server
  2. Login with credentials
  3. Verify login succeeds

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Validation Errors

ErrorDescription
AUTH_FAILEDInvalid username or password
CONNECTION_FAILEDCannot reach the server
TIMEOUTConnection timed out (10 second limit)
HOST_NOT_FOUNDDNS resolution failed
SSL_ERRORSSL/TLS handshake failed
CONNECTION_REFUSEDPort not accepting connections

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Daily Sending Limits

Account AgeRecommended Daily Limit
New (0-2 weeks)20-30 emails/day
Warming (2-4 weeks)50-80 emails/day
Established (4+ weeks)80-100 emails/day

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Why Lower Limits?

Starting with lower limits helps:
  • Build sender reputation
  • Avoid triggering spam filters
  • Maintain high deliverability rates
  • Gradually warm up the account

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Security Recommendations

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Use App Passwords

Always use app-specific passwords instead of your main email password:
  • App passwords have limited scope
  • Can be revoked without changing your main password
  • Required when 2FA is enabled
  • More secure for API integrations

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Never Share Credentials

  • Do not share SMTP/IMAP passwords
  • Revoke app passwords when no longer needed
  • Use unique passwords for each integration

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Monitor Account Activity

Regularly check:
  • Sent folder for unexpected emails
  • Authentication logs in your email provider
  • Account access history