Hi,

on dovecot 2.3.16 with delivery via LMTP I found many of this error when a user have the mailbox full and personal sieve rules:

- lmtp.log:

Sep 14 09:58:27 pop05 dovecot: lmtp(user1@company.com) session=<eAjRDSNWQGFCaQAAP27dBg>: sieve: deliverytime=122, msgid=<000601d7a8f8$fc350d50$f49f27f0$@company.com>, sender=user2@company.com, from=user2@company.com, subject="my subject 1": fileinto action: failed to store into mailbox 'INBOX/Personale': Quota exceeded (mailbox for user is full)
Sep 14 09:58:27 pop05 dovecot: lmtp(user1@company.com) session=<eAjRDSNWQGFCaQAAP27dBg>: sieve: deliverytime=122, msgid=<000601d7a8f8$fc350d50$f49f27f0$@company.com>, sender=user2@company.com, from=user2@company.com, subject="my subject 1": failed to store into mailbox 'INBOX': Quota exceeded (mailbox for user is full)
Sep 14 09:58:27 pop05 dovecot: lmtp(user1@company.com) session=<eAjRDSNWQGFCaQAAP27dBg>: sieve: Execution of script /home/vmail/domains/company.com/user1/.dovecot.sieve failed with unsuccessful implicit keep (user logfile /home/vmail/domains/company.com/user1/.dovecot.sieve.log may reveal additional details)

Sep 14 09:58:27 pop05 dovecot: lmtp(26946): Panic: file mail-user.c: line 229 (mail_user_deinit): assertion failed: ((*user)->refcount == 1)

Sep 14 09:58:27 pop05 dovecot: lmtp(26946): Error: Raw backtrace: /usr/lib64/dovecot/libdovecot.so.0(backtrace_append+0x42) [0x7f52dfb4e632] -> /usr/lib64/dovecot/libdovecot.so.0(backtrace_get+0x1e) [0x7f52dfb4e73e] -> /usr/lib64/dovecot/libdovecot.so.0(+0xf66fe) [0x7f52dfb5c6fe] -> /usr/lib64/dovecot/libdovecot.so.0(+0xf67a1) [0x7f52dfb5c7a1] -> /usr/lib64/dovecot/libdovecot.so.0(i_fatal+0) [
0x7f52dfaaba18] -> /usr/lib64/dovecot/libdovecot-storage.so.0(+0x57567) [0x7f52dfe79567] -> dovecot/lmtp [10.0.2.26 DATA](lmtp_local_data+0x4dc) [0x55e09f333e2c] -> dovecot/lmtp [10.0.2.26 DATA](client_default_cmd_data+0x18b) [0x55e09f33273b] -> dovecot/lmtp [10.0.2.26 DATA](cmd_data_continue+0x204) [0x55e09f3324d4] -> /usr/lib64/dovecot/libdovecot.so.0(+0x5fe64) [0x7f52dfac5e64] -> /usr/li
b64/dovecot/libdovecot.so.0(io_loop_call_io+0x65) [0x7f52dfb74ad5] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x12b) [0x7f52dfb7649b] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_handler_run+0x59) [0x7f52dfb74bd9] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_run+0x38) [0x7f52dfb74e18] -> /usr/lib64/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f52dfadddf3] -> dovecot/lmtp [10.0.2.26 DATA](main+0x20b) [0x55e09f330f0b] -> /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f52df6ba555] -> dovecot/lmtp [10.0.2.26 DATA](+0x6041) [0x55e09f331041]

Sep 14 09:58:27 pop05 dovecot: lmtp(26946): Fatal: master: service(lmtp): child 26946 killed with signal 6 (core dumps disabled - https://dovecot.org/bugreport.html#coredumps)

- sieve.log:

sieve: info: started log at 2021-09-14 10:25:54 +0200.
error: deliverytime=8, msgid=<49ef01d7a942$2168a200$6439e600$@company.com>, sender=sender1@company.com, from=sender1@company.com, subject="I: Undelivered Mail Returned to Sender": fileinto action: failed to store into mailbox 'INBOX/Comunicazioni': Quota exceeded (mailbox for user is full).
error: deliverytime=9, msgid=<49ef01d7a942$2168a200$6439e600$@company.com>, sender=sender1@company.com, from=sender1@company.com, subject="I: Undelivered Mail Returned to Sender": failed to store into mailbox 'INBOX': Quota exceeded (mailbox for user is full).

Hope it can be fixed,

Thanks

-- 
Alessio Cecchi
Postmaster @ http://www.qboxmail.it
https://www.linkedin.com/in/alessice