Efficient processing of time-bound messages is described herein. In an implementation, messages are classified either time-bounded messages or non-time-bounded messages. The time-bounded messages are then processed separately from the non-time-bound messages. Examples of time-bounded messages can include spam e-mails or other types or classes of e-mails subject to a retention policy, such that the are retained only for some set period of time. Metadata relating to the time-bound messages are compiled and stored separately from the messages, thereby enabling optimization of the metadata storage and processing apart from the messages. The time-bounded messages are accumulated before they are processed in bulk, thereby reducing the number if I/O operations consumed by the time-bound messages, and reducing the amount and cost of resources supporting the process of the time-bounded messages.