This should hopefully eliminated errors like:
root@olinda:/etc/postfix# head /var/log/mail/dovecot-deliver.log
2017-11-01 06:43:39 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 06:58:13 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 06:58:13 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:19:39 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:19:39 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:20:45 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:20:45 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:31:56 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:31:56 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
2017-11-01 07:38:38 lda(alex): Error: pwrite_full() failed with file /home/alex/.maildir/.Junk.server/dovecot.index.cache: File too large (process was started with ulimit -f limit)
See also https://wiki.dovecot.org/LDA/Postfix
mailbox_command = /usr/lib/dovecot/deliver
#mailbox_command = /some/where/procmail -a "$EXTENSION"
+# Bump mailbox size limit to 512MB since cache files were maxing out
+# See https://wiki.dovecot.org/LDA/Postfix
+mailbox_size_limit = 512000000
+
# The mailbox_transport specifies the optional transport in master.cf
# to use after processing aliases and .forward files. This parameter
# has precedence over the mailbox_command, fallback_transport and