I'm building an SMS reminder system using Twilio in n8n where agents receive reminders about missing documents for multiple properties. When agents reply via SMS, I cannot identify which property/conversation the reply is referring to because the Message SID changes with each message, breaking conversation continuity.
Business Context
Real estate agents manage multiple properties simultaneously
Agents receive SMS reminders about missing documents for different properties
A single agent can be reminded about 3-5+ properties in the same day
When an agent replies "I'll send it tomorrow", I need to know: Which property are they referring to?
Current Workflow
Outbound SMS Flow (Working)
n8n identifies properties with missing documents
HTTP Request node sends SMS via Twilio API to agent
SMS content: "Hi [Agent], missing documents for [Property Address]. Please upload by [Date]."
Twilio returns Message SID (e.g., SM123abc...)
Message SID stored in database/Google Sheets
Inbound SMS Flow (Broken)
Agent replies: "I'll send the documents tonight"
Twilio webhook triggers n8n with new Message SID (e.g., SM456def...)
Problem: New Message SID has no relationship to original outbound Message SID
Cannot determine: Which property reminder is this reply for?
Attempt : Phone Number Only
Match based on agent phone number alone
Failed: Doesn't work when agent has multiple pending properties
Ideal Solution Criteria
Automatically link SMS replies to specific property reminders
Work reliably even with multiple pending reminders
Minimal friction for agents (simple reply, not complex codes)