[neuhaus]

Horde uses php://temp internally for some APPEND conversions and downloaded content. It starts in memory and normally spills to disk at 2 MB.

The new explicit-length APPEND path creates no payload spool.
With this change, known-length uploads stream directly into one IMAP message, without having to scan or rewind first.

[what-the-diff]

PR Summary

• Adds support for forward-only APPEND streams. Callers can provide a stream and its byte length, allowing data to be sent without seeking or reading ahead. Only the declared number of bytes is consumed, and any remaining source data is preserved.
• Clarifies how to use streams safely. The documentation explains that callers retain ownership of the source, unknown-length inputs must be staged first, and one-pass streams cannot be replayed.
• Improves failure handling. The client validates stream inputs and avoids retrying an APPEND after a one-pass source has been consumed. Short or invalid sources are rejected.
• Adds coverage for the new behavior. Tests check stream consumption, validation, retry limits, BINARY capability checks, and handling of short sources.

[ralflang]

Thank you!