OTM files are used by Microsoft Outlook application for storing sets of macros. Macros in OTM files can be utilized for automating certain repetitive and standardized task related to email processing.

OTM files are written using Visual Basic for Applications scripting language and are take advantage of object-oriented paradigm used by Outlook. Predefined macros can be downloaded from the internet and imported into Outlook, a feature especially useful for less advanced users.