Here is imapsync 1.977 on host privremena, a linux system with 19.3/31.3 free GiB of RAM
with Perl 5.28.1 and Mail::IMAPClient 3.42
Transfer started at Sat Nov  7 15:03:38 2020
PID is 24681 my PPID is 24680
Log file is LOG_imapsync/2020_11_07_15_03_38_038_helpzona@helpzona.com_helpzona@helpzona.com.txt ( to change it, use --logfile path ; or use --nolog to turn off logging )
Load is 0.49 0.65 0.54 1/1195 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 --host1 cp8.ulimitserver.com --host2 91.134.230.68 --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=1
kill -QUIT 24681 # special behavior: call to sub catch_exit
kill -TERM 24681 # special behavior: call to sub catch_exit
kill -INT 24681 # special behavior: call to sub catch_reconnect
kill -HUP 24681 # special behavior: call to sub catch_print
kill -USR1 24681 # 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 24681 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_03_38_038_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 info: authmech [LOGIN] user [helpzona@helpzona.com] authuser [] IsUnconnected []
Host1 failure: Error login on [cp8.ulimitserver.com] with user [helpzona@helpzona.com] auth [LOGIN]: 2 NO [AUTHENTICATIONFAILED] Authentication failed.
Exiting with return value 16 (EXIT_AUTHENTICATION_FAILURE) 1/20 nb_errors/max_errors
Log file is LOG_imapsync/2020_11_07_15_03_38_038_helpzona@helpzona.com_helpzona@helpzona.com.txt ( to change it, use --logfile filepath ; or use --nolog to turn off logging )