What is the difference between an SMS, MMS and app message?¶

SMS is mobile-network text messaging, MMS extends network messaging to media, and app messages use an internet service with its own accounts and provider.

Transport determines the evidence trail¶

Network providers may hold SMS or MMS routing and event records, often without content. App providers may hold account, delivery, device or content records depending on service design and encryption. The handset can retain local databases and notifications for all three.

Identify the actual service used¶

One interface can combine transports, and delivery may switch with connectivity or settings. Record service, account or number, message ID, time and status before deciding which provider to approach or what the artefact means.