Description: ------------ If multiple clients read and modify the same mbox file, then Mail_Mbox corrupts it. This is caused because this start and end byte position change when a mail gets modified. This isn't tracked by Mail_Mbox and the next read and update will destroy the mbox file because of wrong start/end byte position... Reproduce code: --------------- Just run the test supplied in the documentation in a long running loop doing all the same all the while with the open mbox file. Then start mutt and flag a mail as new or old or whatever. The php script must not be in a loop, but imagine it is reading a mbox file at the same moment when mutt edits it. (This is allowed and recommended by the mbox format specs) Expected result: ---------------- A correct mbox file anytime. Actual result: -------------- A corrupted mbox file.

Best solution would be testing if start and end byte positions are valid before reading and writing to mbox. And also request a lock on the mbox file during write operations.