.LSA File Extension
What is an LSA file?
An LSA file is a script created by IBM Lotus Domino Designer. It contains an agent, which is a program that performs a specific task in one or more databases. LSA files include information about the type of agent, where it will run, how it is invoked, what it will act upon, under whose ID it will run, and if it will perform unrestricted or restricted operations.
Agents are similar to scripts because they are used to automate tasks, whether they are database-wide or domain-wide. LSA files are used internally by Lotus Domino Designer to store agents. You will most likely not come across the LSA file but you can build and modify agents through the Domino Designer interface.
NOTE: Domino Designer was originally developed by Lotus Software before Lotus was acquired by IBM in 1995.