Hello,
With my configuration Dovecot creates multiple duplicates (sometimes 2,
sometimes 3, sometimes a plenty) of mailfiles when moving them into the
Sent or the Trash folders. This does not affect the Inbox folder. I
observed this while using Thunderbird on Ubuntu as a client as well as
K9-Mail on Android, therefore I expect this comes from the Dovecot
server and not from the client itself. It also appears that the
duplicates does not have the size S= and vsize W= flags.
Here is a short example of the last emails from my folder /.Sent/cur:
-rw------- 1 pi pi 1,6M mars 24 22:18
1585084691.M834293P16489.raspberry-pi,S=1658182,W=1679758:2,S
-rwx------ 1 pi pi  34M mars 24 22:20
1585084841.M415421P17104Q0Rc311b18de2edf536.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 22:22
1585084954.M254398P17175Q0R6c5a66e22ac3a3d2.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 22:46
1585086411.M317404P18117Q0R61ba34fb281e8eb5.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 22:51
1585086659.M435086P18251Q0R7e118d3bd7784c6d.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 22:53
1585086799.M821376P18319Q0R6b838db7f14a2302.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 22:54
1585086861.M788796P18398Q0Raaa98233db1f9b6a.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:00
1585087244.M616219P18629Q0R4d5856ac0d1b1337.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:01
1585087278.M581756P18651Q0R6a75f871d9e8f0aa.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:01
1585087296.M954701P18666Q0R0cce469807cb0aa8.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:05
1585087552.M557221P18793Q0R541dece72da12039.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:09
1585087759.M768686P18927Q0Rbc1c813e1b124702.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:10
1585087823.M232119P19026Q0R4086d52491835470.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:10
1585087855.M951407P19035Q0R4edd76369b804f54.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:22
1585088561.M364587P19476Q0Rdc0ac3a664f1a80f.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:24
1585088639.M90555P19512Q0R6214b0e915c88908.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:27
1585088859.M192671P19663Q0Re4562fb440f7a4be.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:28
1585088927.M926251P19699Q0Rbe7523140efc06e2.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:29
1585088962.M120826P19721Q0Rd66b5d585c41123b.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:31
1585089111.M427988P19799Q0R5b8e8a032adc33c8.raspberry-pi:2,
-rwx------ 1 pi pi 1,6M mars 24 23:32
1585089138.M910049P19827Q1R1b4d834fadfb0fd6.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:33
1585089180.M811880P19839Q0R8c415b8fbf638018.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:34
1585089252.M333476P19878Q0R3b809c0f458a90e0.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:34
1585089293.M103544P19918Q0Rd9acc8d53f5c8b32.raspberry-pi:2,
-rwx------ 1 pi pi  34M mars 24 23:35
1585089314.M270143P19948Q0R1202a6fe81862880.raspberry-pi:2,
-rw------- 1 pi pi 2,0M mars 29 13:01
1585479708.M437415P11486.raspberry-pi,S=2076767,W=2105374:2,S
-rwx------ 1 pi pi 2,0M mars 29 13:02
1585479733.M94224P13150Q0R974361f29d7d9cdb.raspberry-pi:2,
-rw------- 1 pi pi 2,5K mars 31 09:10
1585638623.M921769P12803.raspberry-pi,S=2511,W=2585:2,S
-rwx------ 1 pi pi 3,0K mars 31 09:11
1585638671.M552885P12861Q0R878fb6aa8485b5c0.raspberry-pi:2,
-rw------- 1 pi pi  19M avril 3 09:38
1585899475.M669440P24679.raspberry-pi,S=19757959,W=20028662:2,S
-rwx------ 1 pi pi  19M avril 3 09:38
1585899531.M744009P25082Q0R0b61c7e8e7b723b4.raspberry-pi:2,
-rw------- 1 pi pi  421 avril 3 14:52
1585918350.M591326P1027.raspberry-pi,S=421,W=434:2,S
-rw------- 1 pi pi  421 avril 3 14:52
1585918360.M206900P1027.raspberry-pi,S=421,W=434:2,S
-rw------- 1 pi pi  421 avril 3 14:52
1585918372.M255849P1032.raspberry-pi,S=421,W=434:2,S
-rwx------ 1 pi pi 1,1K avril 3 14:53
1585918394.M224204P1071Q0R7e9bc28b2d8e7fc4.raspberry-pi:2,
-rwx------ 1 pi pi 1,1K avril 3 14:53
1585918395.M884727P1073Q1Ra4a111c1e0f5a399.raspberry-pi:2,
-rwx------ 1 pi pi 1,1K avril 3 14:53
1585918398.M36019P1077Q2R10960cdc588b3ede.raspberry-pi:2,
Below are details about my configuration
pi@raspberry-pi:~$ sudo uname --all
Linux raspberry-pi 4.4.38+ #938 Thu Dec 15 15:17:54 GMT 2016 armv6l
GNU/Linux
pi@raspberry-pi:~$ mount
[...]
/dev/sda1 on /home/pi type ext4 (rw,noatime,nodiratime,data=ordered)
[...]
pi@raspberry-pi:/var/log$ sudo dovecot --version
2.2.13
pi@raspberry-pi:/var/log$ sudo dovecot -n
# 2.2.13: /etc/dovecot/dovecot.conf
# OS: Linux 4.4.38+ armv6l Debian 8.0 ext4
disable_plaintext_auth = no
mail_location = maildir:/home/pi/Mails/%u
namespace {
 inbox = yes
 location =
 mailbox {
   auto = subscribe
   special_use = \Drafts
   name = Drafts
 }
 mailbox {
   special_use = \Junk
   name = Junk
 }
 mailbox {
   auto = subscribe
   special_use = \Sent
   name = Sent
 }
 mailbox {
   special_use = \Sent
   name = Sent Messages
 }
 mailbox {
   auto = subscribe
   special_use = \Trash
   name = Trash
 }
 prefix =
 separator = /
 type = private
 name = inbox
}
passdb {
 driver = pam
}
passdb {
 args = /home/pi/Mails/dovecot_passwords
 driver = passwd-file
}
protocols = " imap"
service replication-notify-fifo {
 name = aggregator
}
service anvil-auth-penalty {
 name = anvil
}
service auth-worker {
 name = auth-worker
}
service auth-client {
 name = auth
}
service config {
 name = config
}
service dict {
 name = dict
}
service login/proxy-notify {
 name = director
}
service dns-client {
 name = dns_client
}
service doveadm-server {
 name = doveadm
}
service {
 inet_listener {
   address = *
   port = 4143
   name = imap
 }
 name = imap-login
}
service imap-urlauth {
 name = imap-urlauth-login
}
service imap-urlauth-worker {
 name = imap-urlauth-worker
}
service token-login/imap-urlauth {
 name = imap-urlauth
}
service login/imap {
 name = imap
}
service indexer-worker {
 name = indexer-worker
}
service indexer {
 name = indexer
}
service ipc {
 name = ipc
}
service lmtp {
 name = lmtp
}
service log-errors {
 name = log
}
service pop3 {
 name = pop3-login
}
service login/pop3 {
 name = pop3
}
service replicator-doveadm {
 name = replicator
}
service login/ssl-params {
 name = ssl-params
}
service stats-mail {
 name = stats
}
ssl_cert = </home/pi/Mails/imap_ssl_certificate.crt
ssl_key = </home/pi/Mails/imap_ssl_private.key
userdb {
 driver = passwd
}
userdb {
 args = uid=1000 gid=1000 home=/var/mail/%u
 driver = static
}
protocol lmtp {
 service replication-notify-fifo {
   name = aggregator
 }
 service anvil-auth-penalty {
   name = anvil
 }
 service auth-worker {
   name = auth-worker
 }
 service auth-client {
   name = auth
 }
 service config {
   name = config
 }
 service dict {
   name = dict
 }
 service login/proxy-notify {
   name = director
 }
 service dns-client {
   name = dns_client
 }
 service doveadm-server {
   name = doveadm
 }
 service imap {
   name = imap-login
 }
 service imap-urlauth {
   name = imap-urlauth-login
 }
 service imap-urlauth-worker {
   name = imap-urlauth-worker
 }
 service token-login/imap-urlauth {
   name = imap-urlauth
 }
 service login/imap {
   name = imap
 }
 service indexer-worker {
   name = indexer-worker
 }
 service indexer {
   name = indexer
 }
 service ipc {
   name = ipc
 }
 service lmtp {
   name = lmtp
 }
 service log-errors {
   name = log
 }
 service pop3 {
   name = pop3-login
 }
 service login/pop3 {
   name = pop3
 }
 service replicator-doveadm {
   name = replicator
 }
 service login/ssl-params {
   name = ssl-params
 }
 service stats-mail {
   name = stats
 }
}
protocol lda {
 service replication-notify-fifo {
   name = aggregator
 }
 service anvil-auth-penalty {
   name = anvil
 }
 service auth-worker {
   name = auth-worker
 }
 service auth-client {
   name = auth
 }
 service config {
   name = config
 }
 service dict {
   name = dict
 }
 service login/proxy-notify {
   name = director
 }
 service dns-client {
   name = dns_client
 }
 service doveadm-server {
   name = doveadm
 }
 service imap {
   name = imap-login
 }
 service imap-urlauth {
   name = imap-urlauth-login
 }
 service imap-urlauth-worker {
   name = imap-urlauth-worker
 }
 service token-login/imap-urlauth {
   name = imap-urlauth
 }
 service login/imap {
   name = imap
 }
 service indexer-worker {
   name = indexer-worker
 }
 service indexer {
   name = indexer
 }
 service ipc {
   name = ipc
 }
 service lmtp {
   name = lmtp
 }
 service log-errors {
   name = log
 }
 service pop3 {
   name = pop3-login
 }
 service login/pop3 {
   name = pop3
 }
 service replicator-doveadm {
   name = replicator
 }
 service login/ssl-params {
   name = ssl-params
 }
 service stats-mail {
   name = stats
 }
}
protocol imap {
 service replication-notify-fifo {
   name = aggregator
 }
 service anvil-auth-penalty {
   name = anvil
 }
 service auth-worker {
   name = auth-worker
 }
 service auth-client {
   name = auth
 }
 service config {
   name = config
 }
 service dict {
   name = dict
 }
 service login/proxy-notify {
   name = director
 }
 service dns-client {
   name = dns_client
 }
 service doveadm-server {
   name = doveadm
 }
 service imap {
   name = imap-login
 }
 service imap-urlauth {
   name = imap-urlauth-login
 }
 service imap-urlauth-worker {
   name = imap-urlauth-worker
 }
 service token-login/imap-urlauth {
   name = imap-urlauth
 }
 service login/imap {
   name = imap
 }
 service indexer-worker {
   name = indexer-worker
 }
 service indexer {
   name = indexer
 }
 service ipc {
   name = ipc
 }
 service lmtp {
   name = lmtp
 }
 service log-errors {
   name = log
 }
 service pop3 {
   name = pop3-login
 }
 service login/pop3 {
   name = pop3
 }
 service replicator-doveadm {
   name = replicator
 }
 service login/ssl-params {
   name = ssl-params
 }
 service stats-mail {
   name = stats
 }
}