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SMTP Configuration

SendDock uses the BYO-SMTP (Bring Your Own SMTP) model, which means that you provide the email sending provider. This gives you total control over your IP reputation, deliverability, and sending costs.

SMTP Settings

Why BYO-SMTP?​

Advantages​

✅ Total Control: You manage your domain and IP reputation ✅ No Vendor Lock-in: You can change providers whenever you want ✅ Predictable Costs: You pay directly to your SMTP provider, not SendDock for volume ✅ Better Deliverability: Your own verified domain = better reputation ✅ Flexibility: Use different SMTPs for different projects

Disadvantages​

❌ Need to configure and maintain the relationship with the SMTP provider ❌ Must manage your own sending reputation ❌ SMTP costs are additional to SendDock

Recommendation

For most projects, we recommend AWS SES (super economical) or Resend (easier to configure).

Supported Providers​

SendDock works with any standard SMTP provider. The most popular are:

ProviderDifficultyCostBest For
Resend⭐ Easy$20/mo for 50kStartups, rapid development
Hostinger⭐ Easy$3-10/moBlogs, small projects
AWS SES⭐⭐⭐ Complex$0.10 per 1,000High volume, low cost
SendGrid⭐⭐ Medium$20/mo for 50kMarketing and transactional
Mailgun⭐⭐ Medium$35/mo for 50kDevelopers, API-first
Generic SMTP⭐ EasyVariesAny provider

Basic Configuration​

Step 1: Get SMTP Credentials​

From your provider you need:

Host:     smtp.example.com
Port:     587 (or 465, 25)
Username: your-username
Password: your-password

Step 2: Configure in SendDock​

  1. Go to Dashboard → SMTP Settings
  2. Click "Add SMTP Provider"
  3. Complete the form:

SMTP Form

Fields:

  • Provider Name: A descriptive name (e.g., "AWS SES Production")
  • Host: The SMTP server
  • Port: Port (587 recommended for TLS)
  • Username: Your SMTP username
  • Password: Your SMTP password
  • From Email: Email that will appear as sender
  • From Name: Name that will appear as sender
  • Encryption: TLS (recommended) or SSL

Step 3: Verify Configuration​

SendDock includes a Connection Test:

  1. Complete all fields
  2. Click "Test Connection"
  3. SendDock will try to connect and send a test email
  4. If it works, you'll see ✅ "Connection successful"
  5. If it fails, you'll see the specific error for debugging

Test Connection

Common SMTP Ports​

PortDescriptionSecurityRecommended Use
587Submission portSTARTTLS✅ Recommended
465SMTP over SSLSSL/TLS✅ Secure alternative
25Traditional SMTPNone⚠️ Server-to-server only
2525AlternativeSTARTTLS✅ If 587 is blocked
Port 25

Port 25 is usually blocked by hosting providers. Use 587 or 465 instead.

Encryption Types​

TLS (STARTTLS)​

  • Starts without encryption then upgrades to TLS
  • Port: 587 or 2525
  • Recommended for being more compatible

SSL​

  • Encrypted connection from the start
  • Port: 465
  • More secure but less compatible with some providers

None (No encryption)​

  • ⚠️ Not recommended
  • Only for local development or testing
  • Never in production

Advanced Configuration​

Multiple SMTP Providers (Pro+ Plan)​

With the Pro plan or higher, you can configure multiple SMTP providers:

Multiple SMTP

Use cases:

  1. Automatic Failover: If the primary fails, use the backup
  2. Segmentation: Different SMTP for transactional vs marketing
  3. A/B Testing: Compare deliverability between providers
  4. Limits: Distribute load among multiple providers

Configure Failover​

  1. Add your primary SMTP (Priority: 1)
  2. Add a backup SMTP (Priority: 2)
  3. Optionally a third backup (Priority: 3)

When SendDock tries to send:

Attempt 1: SMTP Priority 1
  ↓ (if fails)
Attempt 2: SMTP Priority 2
  ↓ (if fails)
Attempt 3: SMTP Priority 3
  ↓ (if fails)
Error reported
Failover Recommendation
  • SMTP 1: AWS SES (economical, high volume)
  • SMTP 2: Resend (more expensive but super reliable)
  • SMTP 3: SendGrid (final backup)

Domain Verification​

For better deliverability, you must verify your domain with your SMTP provider.

Required DNS Records​

Typically you need to configure:

SPF Record​

TXT @ "v=spf1 include:_spf.example.com ~all"

DKIM Record​

TXT default._domainkey "v=DKIM1; k=rsa; p=MIGfMA0GCS..."

DMARC Record​

TXT _dmarc "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com"
Provider-Specific Guides

Each provider has its own verification process. Check our specific guides:

Email "From" Address​

The sender email must comply with these rules:

✅ Must be verified in your SMTP provider ✅ Use your own domain (e.g., hello@myapp.com) ❌ DO NOT use gmail.com, yahoo.com, outlook.com ❌ DO NOT use noreply@ (looks like spam)

Good examples:

hello@myapp.com
team@myapp.com
notifications@myapp.com
john@myapp.com

Bad examples:

noreply@myapp.com          (Looks like spam)
info@gmail.com             (Can't verify public domains)
DoNotReply@example.com     (Don't be hostile)

From Name​

The "From Name" is the name the recipient sees:

Good examples:

John from MyApp
MyApp Team
MyApp Notifications
MyApp Newsletter

Bad examples:

No Reply                   (Impersonal)
info@myapp.com            (Repeats email)

Credential Security​

Encryption​

SendDock encrypts your SMTP credentials with AES-256 before saving them in the database.

  • ✅ Passwords are encrypted immediately
  • ✅ Only decrypted in memory when sending
  • ✅ SendDock admins CANNOT see your credentials
  • ✅ In backups, credentials remain encrypted

Best Practices​

  1. Don't share credentials between projects if not necessary
  2. Rotate passwords every 3-6 months
  3. Use SMTP keys (API keys) instead of passwords when possible
  4. Revoke access immediately if a team member leaves

Rate Limits​

Each SMTP provider has sending limits:

ProviderLimit per SecondDaily Limit
AWS SES (sandbox)1 email/sec200/day
AWS SES (production)14 emails/secAccording to your quota
Resend (Free)-100/day
Resend (Paid)-50,000+/day
SendGridVariesAccording to plan
Hostinger~100/hour~1,000/day
Respect Limits

SendDock will try to respect provider limits, but you're responsible for monitoring your usage to avoid suspensions.

Monitoring and Logs​

View SMTP Status​

In Dashboard → Logs, you can see:

  • ✅ Successful sends
  • ❌ SMTP connection errors
  • ⚠️ Warnings (soft bounces, delays)
  • 📊 Usage statistics by provider

SMTP Logs

Common Errors​

ErrorCauseSolution
535 Authentication failedIncorrect credentialsVerify username and password
Connection timeoutFirewall or blocked portTry port 2525 or 465
550 Relay not permittedUnverified emailVerify your domain in the provider
Daily sending quota exceededLimit reachedWait 24hrs or upgrade plan

Change SMTP Provider​

You can change your provider at any time:

  1. Configure the new SMTP
  2. Test that it works with "Test Connection"
  3. Mark the new one as Default
  4. Optionally delete the old one
No Impact

Changing SMTP doesn't affect your subscribers, templates, or statistics. It only changes how future emails are sent.

SMTP Debugging​

If emails aren't sending:

1. Verify Connection​

# Manual test with telnet
telnet smtp.example.com 587

2. Check SendDock Logs​

In Dashboard → Logs, look for:

  • Specific error messages
  • Timestamps of failed attempts

3. Check SMTP Provider​

Enter your provider's dashboard and verify:

  • Is your account active?
  • Have you reached any limits?
  • Is your domain verified?
  • Are there security alerts?

4. Test from Command Line​

# Test SMTP with OpenSSL
openssl s_client -starttls smtp -connect smtp.example.com:587

Next Steps​

Configure your specific SMTP provider:

Or continue with: