Here is imapsync 1.977 on host privremena, a linux system with 19.0/31.3 free GiB of RAM
with Perl 5.28.1 and Mail::IMAPClient 3.42
Transfer started at Sat Nov  7 15:13:03 2020
PID is 25104 my PPID is 25103
Log file is LOG_imapsync/2020_11_07_15_13_03_391_helpzona@helpzona.com_helpzona@helpzona.com.txt ( to change it, use --logfile path ; or use --nolog to turn off logging )
Load is 0.22 0.58 0.57 1/1199 on 2 cores
Current directory is /root/imapsync-master
Real user id is root (uid 0)
Effective user id is root (euid 0)
$RCSfile: imapsync,v $ $Revision: 1.977 $ $Date: 2019/12/23 20:18:02 $ 
Command line used, run by /usr/bin/perl:
./imapsync --addheader --automap --dry --host1 cp8.ulimitserver.com --host2 91.134.230.68 --justlogin --password1 MASKED --password2 MASKED --user1 helpzona@helpzona.com --user2 helpzona@helpzona.com
Temp directory is . ( to change it use --tmpdir dirpath )
Under cgi context
Umask set with 0077 (was 0022)
REMOTE_ADDR is ::ffff:89.164.15.130
HTTP_REFERER is http://148.251.112.220:8080/
HTTP_USER_AGENT is Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0
SERVER_SOFTWARE is ./webserver
SERVER_PORT is 8080
HTTP_COOKIE is imapsync_runs=15
kill -QUIT 25104 # special behavior: call to sub catch_exit
kill -TERM 25104 # special behavior: call to sub catch_exit
kill -INT 25104 # special behavior: call to sub catch_reconnect
kill -HUP 25104 # special behavior: call to sub catch_print
kill -USR1 25104 # special behavior: call to sub toggle_sleep
File ./imapsync_cp8.ulimitserver.com_helpzona@helpzona.com_91.134.230.68_helpzona@helpzona.com.pid does not exist
Error reading file ./imapsync_cp8.ulimitserver.com_helpzona@helpzona.com_91.134.230.68_helpzona@helpzona.com.pid : No such file or directory
PID file is ./imapsync_cp8.ulimitserver.com_helpzona@helpzona.com_91.134.230.68_helpzona@helpzona.com.pid ( to change it, use --pidfile filepath ; to avoid it use --pidfile "" )
Writing my PID 25104 in ./imapsync_cp8.ulimitserver.com_helpzona@helpzona.com_91.134.230.68_helpzona@helpzona.com.pid
Writing also my logfile name in ./imapsync_cp8.ulimitserver.com_helpzona@helpzona.com_91.134.230.68_helpzona@helpzona.com.pid : LOG_imapsync/2020_11_07_15_13_03_391_helpzona@helpzona.com_helpzona@helpzona.com.txt
Info: will resync flags for already transferred messages. Use --noresyncflags to not resync flags.
Host1: probing ssl on port 993 ( use --nosslcheck to avoid this ssl probe ) 
Host1: sslcheck detected open ssl port 993 so turning ssl on (use --nossl1 --notls1 to turn off SSL and TLS wizardry)
Host2: probing ssl on port 993 ( use --nosslcheck to avoid this ssl probe ) 
Host2: sslcheck did not detected open ssl port 993. Will use standard 143 port.
SSL debug mode level is --debugssl 1 (can be set from 0 meaning no debug to 4 meaning max debug)
Host1: SSL default mode is like --sslargs1 "SSL_verify_mode=0", meaning for host1 SSL_VERIFY_NONE, ie, do not check the certificate server.
Host1: Use --sslargs1 SSL_verify_mode=1 to have SSL_VERIFY_PEER, ie, check the certificate server of host1
Info: turned ON syncinternaldates, will set the internal dates (arrival dates) on host2 same as host1.
Host1: will try to use LOGIN authentication on host1
Host2: will try to use LOGIN authentication on host2
Host1: imap connection timeout is 120 seconds
Host2: imap connection timeout is 120 seconds
Host1: IMAP server [cp8.ulimitserver.com] port [993] user [helpzona@helpzona.com]
Host2: IMAP server [91.134.230.68] port [143] user [helpzona@helpzona.com]
Host1: connecting and login on host1 [cp8.ulimitserver.com] port [993] with user [helpzona@helpzona.com]
Host1 IP address: 194.146.59.72
Host1 banner: * OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE NAMESPACE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
Host1 capability before authentication: IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE NAMESPACE LITERAL+ AUTH=PLAIN AUTH=LOGIN AUTH
Host1: cp8.ulimitserver.com says it has CAPABILITY for AUTHENTICATE LOGIN
Host1: success login on [cp8.ulimitserver.com] with user [helpzona@helpzona.com] auth [LOGIN]
Host2: connecting and login on host2 [91.134.230.68] port [143] with user [helpzona@helpzona.com]
Host2 IP address: 91.134.230.68
Host2 banner: * OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ STARTTLS AUTH=PLAIN AUTH=LOGIN AUTH=DIGEST-MD5 AUTH=CRAM-MD5] Dovecot (Ubuntu) ready.
Host2 capability before authentication: IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ STARTTLS AUTH=PLAIN AUTH=LOGIN AUTH=DIGEST-MD5 AUTH=CRAM-MD5 AUTH
Host2: going to ssl because STARTTLS is in CAPABILITY. Use --notls1 or --notls2 to avoid that behavior
DEBUG: .../IO/Socket/SSL.pm:825: local error: SSL connect attempt failed error:1408F10B:SSL routines:ssl3_get_record:wrong version number
DEBUG: .../IO/Socket/SSL.pm:828: fatal SSL error: SSL connect attempt failed error:1408F10B:SSL routines:ssl3_get_record:wrong version number
Host2 failure: Can not go to tls encryption on host2 [91.134.230.68]:Unable to start TLS: SSL connect attempt failed error:1408F10B:SSL routines:ssl3_get_record:wrong version number
Exiting with return value 12 (EXIT_TLS_FAILURE) 1/20 nb_errors/max_errors
Disconnecting from host1 cp8.ulimitserver.com user1 helpzona@helpzona.com
Log file is LOG_imapsync/2020_11_07_15_13_03_391_helpzona@helpzona.com_helpzona@helpzona.com.txt ( to change it, use --logfile filepath ; or use --nolog to turn off logging )