SMTP Configuration

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Prerequisites

• Postfix mail server (installed with PHP stack)
• SMTP service credentials (Gmail, SendGrid, Mailgun, etc.)
• A valid domain name configured on your server

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Install Postfix

sudo stack -php

sudo stack -postfix

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Configure SMTP

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Interactive Setup

sudo webinoly -smtp

1. SMTP Host: Your email provider’s SMTP server (e.g., smtp.gmail.com)
2. User: SMTP username or email address
3. Password: SMTP password or app-specific password
4. Main Hostname/Domain: Your primary domain for sending emails

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Non-Interactive Setup

sudo webinoly -smtp=[smtp.example.com,[email protected],password,example.com]

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SMTP Provider Examples

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Gmail

1. Enable 2-factor authentication on your Google account
2. Generate an app-specific password: https://myaccount.google.com/apppasswords
3. Configure Webinoly:

sudo webinoly -smtp=[smtp.gmail.com,[email protected],app-password,yourdomain.com]

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SendGrid

1. Create a SendGrid account and API key
2. Configure:

sudo webinoly -smtp=[smtp.sendgrid.net,apikey,your-api-key,yourdomain.com]

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Mailgun

1. Create Mailgun account and obtain SMTP credentials
2. Configure:

sudo webinoly -smtp=[smtp.mailgun.org,[email protected],smtp-password,yourdomain.com]

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Amazon SES

1. Create SMTP credentials in AWS SES console
2. Configure:

sudo webinoly -smtp=[email-smtp.us-east-1.amazonaws.com,AWS-ACCESS-KEY,AWS-SECRET-KEY,yourdomain.com]

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Postmark

sudo webinoly -smtp=[smtp.postmarkapp.com,your-server-token,your-server-token,yourdomain.com]

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Brevo (Sendinblue)

sudo webinoly -smtp=[smtp-relay.brevo.com,[email protected],smtp-key,yourdomain.com]

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Configuration Files

myhostname = yourdomain.com
myorigin = /etc/mailname
relayhost = smtp.example.com:587

smtp.example.com:587 [email protected]:password

yourdomain.com

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Main Hostname

• The FROM domain for system emails
• Server’s mail identity
• Default origin for outgoing mail

• Must be a valid domain configured on your server
• Should match a site in /etc/nginx/sites-available/
• Recommended: Configure SPF and DKIM records for this domain

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Test Email Delivery

# Send test email
echo "Test email from Webinoly" | mail -s "Test Subject" [email protected]

# Check mail queue
mailq

# View mail log
sudo log -mail

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Monitor Email Logs

# Real-time mail logs
sudo log -mail

# Or
sudo log -email

# Check for errors
sudo tail -f /var/log/mail.err

• status=sent - Email sent successfully
• status=deferred - Temporary failure, will retry
• status=bounced - Permanent failure

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WordPress Integration

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Configure wp-mail-smtp Plugin

1. Install WP Mail SMTP plugin
2. Configure with “Other SMTP” option:
   • SMTP Host: localhost
   • SMTP Port: 25
   • Encryption: None
   • Authentication: Off

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Alternative: Direct SMTP in WordPress

1. Install WP Mail SMTP plugin
2. Enter your SMTP provider credentials
3. This bypasses Postfix (not recommended - use Webinoly SMTP instead)

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Troubleshooting

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Emails Not Sending

1. Check Postfix status:
   sudo systemctl status postfix
   
2. Test SMTP credentials:
   # Test authentication
   sudo postfix check
   sudo postfix reload
   
3. Verify SMTP host is reachable:
   telnet smtp.example.com 587
   
4. Check mail queue:
   mailq
   
5. View detailed logs:
   sudo tail -100 /var/log/mail.log
   

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Authentication Failures

1. Verify credentials are correct
2. Check if app-specific password is needed (Gmail)
3. Ensure SMTP user has sending permissions
4. Regenerate SMTP password/API key

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DNS/SPF Issues

1. Add SPF record to main hostname domain:
   v=spf1 include:_spf.google.com ~all
   
   (Adjust based on SMTP provider)
2. Configure DKIM if supported by provider
3. Set up DMARC policy:
   v=DMARC1; p=none; rua=mailto:[email protected]
   

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Firewall Blocking Port 587

# Check if port 587 is blocked
sudo ufw status

# Allow outgoing SMTP
sudo ufw allow out 587/tcp

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Queue Not Processing

# Force queue processing
sudo postqueue -f

# Remove specific messages
sudo postsuper -d MESSAGE_ID

# Remove all queued messages
sudo postsuper -d ALL

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Backup SMTP Configuration

sudo webinoly -backup=export -server

sudo cp /etc/postfix/main.cf /root/main.cf.backup
sudo cp /etc/postfix/sasl_passwd /root/sasl_passwd.backup
sudo cp /etc/mailname /root/mailname.backup

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Disable SMTP

# Restore from template
sudo cp /opt/webinoly/templates/source/main.cf /etc/postfix/main.cf

# Remove credentials
sudo rm /etc/postfix/sasl_passwd*

# Restart Postfix
sudo systemctl restart postfix

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Security Best Practices

1. Use App-Specific Passwords: Don’t use main account passwords
2. Rotate Credentials: Change SMTP passwords regularly
3. Monitor Logs: Watch for unauthorized sending attempts
4. Rate Limiting: Most providers limit sending rates
5. SPF/DKIM/DMARC: Configure email authentication
6. Restrict Access: Keep sasl_passwd file secure (already 0600)

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Advanced Configuration

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Custom Postfix Settings

sudo nano /etc/postfix/main.cf

# Set message size limit (50MB)
message_size_limit = 52428800

# Set mailbox size limit
mailbox_size_limit = 0

# Set sender address
smtp_generic_maps = hash:/etc/postfix/generic

sudo systemctl reload postfix

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Multiple SMTP Relays

# Edit sender-dependent relay map
sudo nano /etc/postfix/sender_relay

[email protected]    [smtp.provider1.com]:587
[email protected]    [smtp.provider2.com]:587

sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay

sudo postmap /etc/postfix/sender_relay
sudo systemctl reload postfix