Here is a patch to fix the problem where an imap process runs away when imap-zlib is in use. The backtrace showed: io_loop_handler_run -> stream_send_io -> client_output -> o_stream_flush -> o_stream_zlib_flush -> o_stream_zlib_send_flush When o_stream_zlib_flush returns 0, stream_send_io reinstates the IO_WRITE event, causing the infinite loop. diff -ur dovecot-2.0.beta4/src/plugins/zlib/ostream-bzlib.c dovecot-2.0.beta4+fix/src/plugins/zlib/ostream-bzlib.c --- dovecot-2.0.beta4/src/plugins/zlib/ostream-bzlib.c 2010-02-12 20:22:07.000000000 -0600 +++ dovecot-2.0.beta4+fix/src/plugins/zlib/ostream-bzlib.c 2010-04-20 19:15:29.000000000 -0500 @@ -122,15 +122,15 @@ static int o_stream_bzlib_flush(struct ostream_private *stream) { struct bzlib_ostream *zstream = (struct bzlib_ostream *)stream; + int ret; if (o_stream_bzlib_send_flush(zstream) < 0) return -1; - if (o_stream_flush(zstream->output) < 0) { + ret = o_stream_flush(zstream->output); + if (ret < 0) zstream_copy_error(zstream); - return -1; - } - return 0; + return ret; } static ssize_t diff -ur dovecot-2.0.beta4/src/plugins/zlib/ostream-zlib.c dovecot-2.0.beta4+fix/src/plugins/zlib/ostream-zlib.c --- dovecot-2.0.beta4/src/plugins/zlib/ostream-zlib.c 2010-02-18 22:01:56.000000000 -0600 +++ dovecot-2.0.beta4+fix/src/plugins/zlib/ostream-zlib.c 2010-04-20 19:15:29.000000000 -0500 @@ -184,15 +184,15 @@ static int o_stream_zlib_flush(struct ostream_private *stream) { struct zlib_ostream *zstream = (struct zlib_ostream *)stream; + int ret; if (o_stream_zlib_send_flush(zstream) < 0) return -1; - if (o_stream_flush(zstream->output) < 0) { + ret = o_stream_flush(zstream->output); + if (ret < 0) zstream_copy_error(zstream); - return -1; - } - return 0; + return ret; } static ssize_t