I upgraded (NetBSD 2.99 i386) from 1.0rc7 to 1.0rc24 and then tried rc25, and in both cases need to restart Dovecot every day or so (low volume server). It seems to run out of file descriptors. I have now raised the file descriptor limit to 1024, but that is not a long-term solution...
...
Mar 5 11:41:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:42:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:43:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:44:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:46:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:47:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:48:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:49:38 arioch dovecot: pipe() failed: Too many open files
Mar 5 11:50:38 arioch dovecot: pipe() failed: Too many open files
...lsof(1) output for dovecot-auth and dovecot:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dovecot-a 22627 root cwd VDIR 0,6 512 405514 /var/run/dovecot
dovecot-a 22627 root txt VREG 0,5 175256 1083551 /usr (/dev/wd0f)
dovecot-a 22627 root txt VREG 0,5 7399 101747 /usr/lib/libcom_err.so.4.1
dovecot-a 22627 root txt VREG 0,0 1083908 67635 /lib/libcrypto.so.2.1
dovecot-a 22627 root txt VREG 0,0 866469 67587 /lib/libc.so.12.125
dovecot-a 22627 root txt VREG 0,0 24557 67605 /lib/libcrypt.so.0.2
dovecot-a 22627 root txt VREG 0,5 52783 101743 /usr/lib/libroken.so.12.3
dovecot-a 22627 root txt VREG 0,5 41436 101739 /usr/lib/libdes.so.7.0
dovecot-a 22627 root txt VREG 0,5 145345 101759 /usr/lib/libasn1.so.6.1
dovecot-a 22627 root txt VREG 0,5 251589 102046 /usr/lib/libkrb5.so.19.1
dovecot-a 22627 root txt VREG 0,5 66856 101775 /usr/lib/libgssapi.so.5.0
dovecot-a 22627 root txt VREG 0,0 56172 101377 /libexec/ld.elf_so
dovecot-a 22627 root 0u unix 0xc0f773c4 0t0 ->0xc115a144
dovecot-a 22627 root 1r VCHR 2,2 0t0 45067 /dev/null
dovecot-a 22627 root 2w PIPE 0xcb000e10 0 ->0xcb000d80
dovecot-a 22627 root 3u unix 0xc0f9fbe4 0t0 /var/run/dovecot/login/default
dovecot-a 22627 root 4u KQUEUE 0xc0f11c30
dovecot-a 22627 root 5r VCHR 46,1 0t4 45571 /dev/urandom
dovecot-a 22627 root 6r PIPE 0xcb0006c0 16384 ->0xcc08b2d0
dovecot-a 22627 root 7w PIPE 0xcc08b2d0 0 ->0xcb0006c0
dovecot-a 22627 root 12r VCHR 46,1 0t1024 45571 /dev/urandom
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dovecot 5161 root cwd VDIR 0,6 512 405514 /var/run/dovecot
dovecot 5161 root txt VREG 0,5 119872 1109297 /usr (/dev/wd0f)
dovecot 5161 root txt VREG 0,0 866469 67587 /lib/libc.so.12.125
dovecot 5161 root txt VREG 0,0 56172 101377 /libexec/ld.elf_so
dovecot 5161 root 0r VCHR 2,2 0t0 45067 /dev/null
dovecot 5161 root 1r VCHR 2,2 0t0 45067 /dev/null
dovecot 5161 root 2r VCHR 2,2 0t0 45067 /dev/null
dovecot 5161 root 3r VCHR 2,2 0t0 45067 /dev/null
dovecot 5161 root 4r VCHR 2,2 0t0 45067 /dev/null
dovecot 5161 root 5u IPv4 0xc0f13500 0t0 TCP *:imap (LISTEN)
dovecot 5161 root 6u KQUEUE 0xc0f11410
dovecot 5161 root 7u unix 0xc0d3cd80 0t0 ->0xc0d3c0d8
dovecot 5161 root 8r PIPE 0xcb000a20 16384 ->0xcb000cf0
dovecot 5161 root 9w PIPE 0xcb000cf0 0 ->0xcb000a20
dovecot 5161 root 10u unix 0xc0f15bd4 0t0 /var/run/dovecot/dict-server
dovecot 5161 root 11u unix 0xc0f9fbe4 0t0 /var/run/dovecot/login/default
dovecot 5161 root 12u unix 0xc115a144 0t0 ->0xc0f773c4
dovecot 5161 root 14r PIPE 0xcb000900 16384
dovecot 5161 root 16r PIPE 0xcb000d80 16384 ->0xcb000e10
dovecot 5161 root 17r PIPE 0xcd4a7994 16384
dovecot 5161 root 18r PIPE 0xcd4a7bd4 16384
dovecot 5161 root 19r PIPE 0xcd659634 16384
dovecot 5161 root 20r PIPE 0xcb000870 16384
dovecot 5161 root 21r PIPE 0xcd4a7c64 16384
dovecot 5161 root 22r PIPE 0xcd4a7cf4 16384
dovecot 5161 root 23r PIPE 0xce11dac4 16384
dovecot 5161 root 24r PIPE 0xce11d914 16384
dovecot 5161 root 25r PIPE 0xcd4a71b4 16384
dovecot 5161 root 26r PIPE 0xce11d644 16384
dovecot 5161 root 27r PIPE 0xcd6592d4 16384
dovecot 5161 root 28r PIPE 0xcd659094 16384
dovecot 5161 root 29r PIPE 0xcd659874 16384
dovecot 5161 root 30r PIPE 0xcb000990 16384
dovecot 5161 root 31r PIPE 0xce11d374 16384
dovecot 5161 root 32r PIPE 0xce11d254 16384
dovecot 5161 root 33r PIPE 0xce11d764 16384
dovecot 5161 root 34r PIPE 0xcd4a72d4 16384
dovecot 5161 root 35r PIPE 0xce11de24 16384
dovecot 5161 root 36r PIPE 0xce11d404 16384
dovecot 5161 root 37r PIPE 0xce11d9a4 16384
dovecot 5161 root 38r PIPE 0xcd659754 16384
dovecot 5161 root 39r PIPE 0xcd659c64 16384
dovecot 5161 root 40r PIPE 0xcc08b5a0 16384
dovecot 5161 root 41r PIPE 0xcc08b870 16384
dovecot 5161 root 42r PIPE 0xcc08b360 16384
dovecot 5161 root 43r PIPE 0xcc08bc60 16384
dovecot 5161 root 44r PIPE 0xcc08bab0 16384
dovecot 5161 root 45r PIPE 0xcc08b000 16384
dovecot 5161 root 46r PIPE 0xcc08b120 16384
dovecot 5161 root 47r PIPE 0xcc08b6c0 16384
dovecot 5161 root 48r PIPE 0xcc08b990 16384
dovecot 5161 root 49u unix 0xc0f77214 0t0 /var/run/dovecot/auth-worker.22627
dovecot 5161 root 50r PIPE 0xcc08b630 16384
dovecot 5161 root 51r PIPE 0xcc08b240 16384
dovecot 5161 root 52r PIPE 0xcc08bbd0 16384
dovecot 5161 root 53r PIPE 0xcc08b750 16384
dovecot 5161 root 54r PIPE 0xcc08b900 16384
dovecot 5161 root 55r PIPE 0xcc08bb40 16384
dovecot 5161 root 56r PIPE 0xcccd5018 16384
dovecot 5161 root 57r PIPE 0xcc08b1b0 16384
dovecot 5161 root 58r PIPE 0xcccd5528 16384
dovecot 5161 root 59r PIPE 0xcccd52e8 16384
dovecot 5161 root 60r PIPE 0xcd659514 16384
dovecot 5161 root 61r PIPE 0xcccd5138 16384
dovecot 5161 root 62r PIPE 0xcccd59a8 16384
-- Viktor.