📌 Purpose & Quick Summary

Beyond standard mailboxes, BoostonCP provides flexible routing capabilities: Email Forwarders to route incoming messages to Gmail or Outlook, Catch-All Mailboxes to intercept misaddressed emails, and External SMTP Relay integration to route outbound emails through enterprise delivery networks (such as SendGrid, Amazon SES, or Mailgun) with 100% inbox deliverability.

BoostonCP Email Forwarders & Aliases

Figure 16.1: Email forwarders management showing alias mapping rules and target destinations.

🖥️ Interface Tour & Elements

  1. Forwarders Tab: Configure alias addresses that automatically forward copies of incoming mail to external or internal recipient addresses.
  2. Catch-All Tab: Directs any email sent to non-existent addresses on your domain ([email protected]) to a designated mailbox or rejects them with a bounce message.
  3. SMTP Relay Tab: Allows routing outbound mail through external authenticated SMTP smarthosts (SendGrid, Mailgun, Amazon SES).
BoostonCP SMTP Relay Configuration

Figure 16.2: Outbound SMTP relay configuration for integrating third-party delivery providers.

🛠️ Step-by-Step Instructions

Step 1: Creating an Email Forwarder

  1. In the Email Accounts page, click the Forwarders tab.
  2. Click Add Forwarder.
  3. In Source Address, enter [email protected].
  4. In Destination Email, enter your personal address (e.g. [email protected]).
  5. Click Create Forwarder. Incoming messages are immediately forwarded without retaining server storage.

Step 2: Configuring an External SMTP Relay

  1. Click the SMTP Relay tab.
  2. Toggle Enable External Relay to ON.
  3. Enter your provider's credentials:
    • SMTP Host: e.g. smtp.sendgrid.net or email-smtp.us-east-1.amazonaws.com.
    • Port: 587 (TLS) or 465 (SSL).
    • Username: apikey (or provider username).
    • Password: Your provider's API key.
  4. Click Save Relay Configuration. Outbound mail now bypasses local Port 25 and delivers via the relay.

⚙️ Complete Field & Parameter Reference Table

Feature / Setting Description Recommended Usage
Email Forwarder Redirects email to one or multiple destinations. Use for department aliases (sales@ -> multiple team members).
Catch-All: Forward Routes all unassigned mail to a single mailbox. Catches misspellings from customers.
Catch-All: Blackhole / Reject Drops unassigned mail with bounce notice. Recommended: Prevents dictionary spam attacks from filling disk.
SMTP Relay Host Third-party SMTP server hostname. Guaranteed 100% inbox delivery and IP reputation protection.

❓ Troubleshooting & Common Errors

1. Gmail Rejects Forwarded Emails with "DMARC Policy Violation"

  • Cause: Forwarded emails retain original sender headers without SRS (Sender Rewriting Scheme), failing SPF at Gmail.
  • Solution: In BoostonCP, SRS is enabled by default. Ensure the destination domain is not blocking forwarded headers, or create a native mailbox and use Gmail's POP3 Fetcher instead.