Resource Usage

These settings are useful to prevent IMAP commands from opening too many emails and causing larger system-wide performance problems.

mail_sort_max_read_count = 100

This controls how many slow mail accesses sorting can perform before it fails with: NO [LIMIT] Requested sort would have taken too long. The SORT reply is still returned, but it’s likely not correct.

As an exception with the obox format, SORT (ARRIVAL) will always return OK. When it reaches the limit, it starts getting the received-timestamps from the time the object was saved. This is commonly the same as the received-timestamp, but not always.

protocol !indexer-worker {
  mail_vsize_bg_after_count = 100

If more than this many mails need to be opened/stat()ed to get their vsize, return failure and finish up the quota recalculation on background. When a quota failure happens during LMTP delivery or IMAP APPEND/COPY, user is assumed to be below quota and the operation will succeed. Only the IMAP GETQUOTA command will return a failure

plugin {
  mail_log_cached_only = yes

If enabled, everything except save event will log only the fields that can be looked up from cache. This improves performance if some of the fields aren’t cached and it’s not a strict requirement to log them.

import_environment = $import_environment MALLOC_MMAP_THRESHOLD_=131072

Avoid processes permanently using too much memory by having it use mmap() for >=128 kB memory allocations.