Abstract: Among other things, one or more techniques and/or systems are provided for synchronizing a text message, such as an MMS message and/or an SMS message, in full fidelity between a computing device and a message synchronization service. That is, content, natively supported by message synchronization protocols, and extended properties, not natively supported by message synchronization protocols, of a text message may be synchronized between a computing device and a message synchronization service. In particular, a message synchronization protocol may be modified to support annotations and/or extended headers, within which one or more extended properties may be specified. In this way, a synchronization message may comprise natively supported content and/or an extended property specified within an annotation and/or an extended header within the synchronization message.