The "imap" process of dovecot-2.0.beta[5,6] grows very large (I impose no system limits), e.g. exceeding 4.8GB on a 64-bit system. These messages appear in the logs: Warning: Growing pool 'imap client' with: 2048 Warning: Growing pool 'Cache fields' with: 2048 Warning: Growing data stack with: 32768 Warning: Growing data stack with: 65536 Warning: Growing data stack with: 131072 [...] Warning: Growing data stack with: 1073741824 Warning: Growing data stack with: 2147483648 Warning: Growing data stack with: 4294967296 Every time the data stack grows, the backtrace ends with either: 2 libdovecot.0.dylib 0x00000001059a35c3 pool_data_stack_realloc + 72 -> 3 libdovecot.0.dylib 0x0000000105994d59 buffer_alloc + 59 -> 4 libdovecot.0.dylib 0x0000000105994ef9 buffer_check_limits + 127 -> 5 libdovecot.0.dylib 0x00000001059950e8 buffer_append + 38 -> 6 imap 0x0000000105867333 imap_refresh_proctitle + 218 -> 7 imap 0x000000010585f18e client_command_input + 190 -> [...] or 2 libdovecot.0.dylib 0x00000001059a35c3 pool_data_stack_realloc + 72 -> 3 libdovecot.0.dylib 0x0000000105994d59 buffer_alloc + 59 -> 4 libdovecot.0.dylib 0x0000000105994ef9 buffer_check_limits + 127 -> 5 libdovecot.0.dylib 0x00000001059950e8 buffer_append + 38 -> 6 imap 0x0000000105867333 imap_refresh_proctitle + 218 -> 7 imap 0x00000001058666ce cmd_sync_continue + 199 -> [...] Here is a patch to fix it: --- a/src/imap/main.c (beta6) +++ b/src/imap/main.c (working copy) @@ -39,11 +39,12 @@ #define IMAP_PROCTITLE_PREFERRED_LEN 80 struct client *client; struct client_command_context *cmd; - string_t *title = t_str_new(128); + string_t *title; if (!verbose_proctitle) return; + title = str_new(default_pool, 128); str_append_c(title, '['); switch (imap_client_count) { case 0: @@ -72,6 +73,7 @@ } str_append_c(title, ']'); process_title_set(str_c(title)); + str_free(&title); } static void client_kill_idle(struct client *client) And perhaps there should be a warning when data is allocated out of the primordial data stack (as opposed to a nested one)?