I updated my IMAP stress testing tool to support also APPENDs and print some nice statistics. If you want to try for yourself, it's here: http://dovecot.org/tools/imaptest.c I thought about adding some more features in future to it, such as: - Add a header to each appended message containing MD5 sum of it. When fetching, verify that the MD5 sum is valid. - Do randomized fetch requests (headers, size, flags, etc.) - Do randomized search requests - sort, thread