Here is imapsync 1.977 on host privremena, a linux system with 17.2/31.3 free GiB of RAM
with Perl 5.28.1 and Mail::IMAPClient 3.42
Transfer started at Wed Jul 29 12:41:38 2020
PID is 13032 my PPID is 13031
Log file is LOG_imapsync/2020_07_29_12_41_38_758_office@green-line.co.rs_tester@ranitovic.in.rs.txt ( to change it, use --logfile path ; or use --nolog to turn off logging )
Load is 0.71 0.51 0.38 1/1181 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 cp8.ulimitserver.com --password1 MASKED --password2 MASKED --user1 office@green-line.co.rs --user2 tester@ranitovic.in.rs
Temp directory is . ( to change it use --tmpdir dirpath )
Under cgi context
Umask set with 0077 (was 0022)
REMOTE_ADDR is ::ffff:89.216.99.93
HTTP_REFERER is http://148.251.112.220:8080/
HTTP_USER_AGENT is Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0
SERVER_SOFTWARE is ./webserver
SERVER_PORT is 8080
HTTP_COOKIE is 686c9b6492d74d6d7c41621a12c6956f=la6q3dnkojbe6vjjq7boesovf2
kill -QUIT 13032 # special behavior: call to sub catch_exit
kill -TERM 13032 # special behavior: call to sub catch_exit
kill -INT 13032 # special behavior: call to sub catch_reconnect
kill -HUP 13032 # special behavior: call to sub catch_print
kill -USR1 13032 # special behavior: call to sub toggle_sleep
File ./imapsync_cp8.ulimitserver.com_office@green-line.co.rs_cp8.ulimitserver.com_tester@ranitovic.in.rs.pid does not exist
Error reading file ./imapsync_cp8.ulimitserver.com_office@green-line.co.rs_cp8.ulimitserver.com_tester@ranitovic.in.rs.pid : No such file or directory
PID file is ./imapsync_cp8.ulimitserver.com_office@green-line.co.rs_cp8.ulimitserver.com_tester@ranitovic.in.rs.pid ( to change it, use --pidfile filepath ; to avoid it use --pidfile "" )
Writing my PID 13032 in ./imapsync_cp8.ulimitserver.com_office@green-line.co.rs_cp8.ulimitserver.com_tester@ranitovic.in.rs.pid
Writing also my logfile name in ./imapsync_cp8.ulimitserver.com_office@green-line.co.rs_cp8.ulimitserver.com_tester@ranitovic.in.rs.pid : LOG_imapsync/2020_07_29_12_41_38_758_office@green-line.co.rs_tester@ranitovic.in.rs.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 detected open ssl port 993 so turning ssl on (use --nossl2 --notls2 to turn off SSL and TLS wizardry)
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
Host2: SSL default mode is like --sslargs2 "SSL_verify_mode=0", meaning for host2 SSL_VERIFY_NONE, ie, do not check the certificate server.
Host2: Use --sslargs2 SSL_verify_mode=1 to have SSL_VERIFY_PEER, ie, check the certificate server of host2
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 [office@green-line.co.rs]
Host2: IMAP server [cp8.ulimitserver.com] port [993] user [tester@ranitovic.in.rs]
Host1: connecting and login on host1 [cp8.ulimitserver.com] port [993] with user [office@green-line.co.rs]
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 [office@green-line.co.rs] auth [LOGIN]
Host2: connecting and login on host2 [cp8.ulimitserver.com] port [993] with user [tester@ranitovic.in.rs]
Host2 IP address: 194.146.59.72
Host2 banner: * OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE NAMESPACE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
Host2 capability before authentication: IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE NAMESPACE LITERAL+ AUTH=PLAIN AUTH=LOGIN AUTH
Host2: cp8.ulimitserver.com says it has CAPABILITY for AUTHENTICATE LOGIN
Host2 info: authmech [LOGIN] user [tester@ranitovic.in.rs] authuser [] IsUnconnected []
Host2 failure: Error login on [cp8.ulimitserver.com] with user [tester@ranitovic.in.rs] auth [LOGIN]: 2 NO [AUTHENTICATIONFAILED] Authentication failed.
Exiting with return value 16 (EXIT_AUTHENTICATION_FAILURE) 1/20 nb_errors/max_errors
Disconnecting from host1 cp8.ulimitserver.com user1 office@green-line.co.rs
Log file is LOG_imapsync/2020_07_29_12_41_38_758_office@green-line.co.rs_tester@ranitovic.in.rs.txt ( to change it, use --logfile filepath ; or use --nolog to turn off logging )