How OutboundSync formats Email Replies in HubSpot

Overview

This article explains how OutboundSync processes and formats email replies before syncing them into HubSpot. The goal of our approach is to maximize data retention and reliability, even if that sometimes comes at the expense of perfect readability.

High-Level Philosophy

When syncing email data into HubSpot, OutboundSync intentionally errs on the side of preserving as much original data as possible.

As a guiding principle:

The problem is the myriad of characters that can create issues, break the API call, and result in data loss. We have erred on the side of getting the data into HubSpot.

Because of this, our formatting and cleanup logic is conservative. We avoid aggressive sanitization or transformations that could result in truncated payloads, failed API calls, or lost message content.

Source Payload (example shown: Smartlead – EMAIL_REPLY)

OutboundSync consumes the EMAIL_REPLY event payload from the sequencer. The relevant structure includes both html and text representations of the message:

{ event_type: 'EMAIL_REPLY';
  subject: string;
  to_name: string;
  to_email: string;
  from_email: string;
  campaign_name: string;
  campaign_id: string;
  sl_email_lead_id: string;
  client_id: string;
  message_id: string;
  sent_message: {
    text: string;
    html: string;
    message_id: string;
  };
  reply_message: {
    html: string;
    text: string;
    message_id: string;
  };
  sequence_number: string;
  stats_id: string;
  event_timestamp: string;
}

Which Fields We Use in HubSpot

Primary Field: reply_message.html

Deprecated Field: reply_message.text

Why we stopped using reply_message.text:

To prevent this, we now prefer HTML-based syncing whenever possible.

Handling Missing HTML in the Payload

While reply_message.html is our preferred field, the payload does not always populate it.

Current Fallback Logic

When this happens:

This logic ensures we do not drop replies simply because HTML content is missing.

Why Formatting May Look "Messy" in HubSpot

Some email replies in HubSpot may contain:

This is expected behavior.

We intentionally avoid aggressive cleanup because:

Summary

If you see formatting artifacts in HubSpot, it is usually a sign that OutboundSync successfully preserved the full reply rather than risking partial data.