Lmtp Memory Limit

[Thomas Manninger]

Hi,
 
i am using dovecot 2.2.33.2 on CentOS 7.4.
 
Since i upgraded from CentOS 7.2. to CentOS 7.4. (without upgrading dovecot), my dovecot sieve-pipe scripts crash with Out of memory:
Out of memory (allocated 262144) (tried to allocate 8793 bytes)
 
There are some memory limits in dovecot or sieve? Can i change this value?
 
Kernel limitks:
[root at xxx software]# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 26505
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 26505
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
 
 
Dovecot is running as user mail:
 su mail
bash-4.2$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 26505
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4096
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
 
Can someone help me?

Thanks for help!
 
Best regards
Thomas Manninger