Lambda Multi-Recipient Email Processing Fix

The Problem

Our Lambda function was failing to process emails when they were sent to multiple recipients across different domains. The function would only check the first recipient's domain when searching for emails in S3, causing failures for BCC'd emails or emails sent to multiple domains.

What Changed

Enhanced Domain Detection

The Lambda now considers all recipients when determining where to search for emails:

• Extracts recipients from To, CC, and BCC fields
• Identifies all unique domains across recipients
• Searches all possible S3 locations until the email is found

Improved Error Handling

• Better logging shows all recipients and domains being checked
• More descriptive error messages when emails can't be found
• Includes recipient information in error logs for easier debugging

Technical Details

Previously, the Lambda used this logic:

const recipientEmail = recipients[0] || '';
const domain = recipientEmail.split('@')[1] || '';

Now it uses comprehensive recipient detection:

const allEmails = [...new Set([
  ...allRecipients,
  ...toRecipients.map(r => typeof r === 'string' ? r : r.address),
  ...ccRecipients.map(r => typeof r === 'string' ? r : r.address),
  ...bccRecipients.map(r => typeof r === 'string' ? r : r.address)
])];

const domains = [...new Set(
  allEmails.map(email => email.match(/@([^@\s]+)$/)?.[1]).filter(Boolean)
)];

Impact

This fix ensures that:

• Emails sent as BCC are properly processed
• Multi-domain email scenarios work correctly
• Email forwarding is more reliable across complex recipient configurations

No action is required from users - this fix is automatically deployed to all Lambda functions.