Error when trying to send message
Failed to send mail, error reason [(535, b'5.7.8 Error: authentication failed: UGFzc3dvcmQ6')]

Here is the logs :
Sep 17 02:11:32 mail postfix/smtpd[34723]: disconnect from localhost[::1] ehlo=1 auth=0/2 commands=1/3
Sep 17 02:14:30 mail dovecot[34644]: imap-login: Aborted login (auth failed, 2 attempts in 14 secs): user=<root>, method=PLAIN, rip=::1, lip=::1, TLS, session=<Z/HXzyXMmpUAAAAAAAAAAAAAAAAAAAAB>
Sep 17 02:14:58 mail dovecot[34644]: imap-login: Aborted login (auth failed, 2 attempts in 14 secs): user=<root>, method=PLAIN, rip=::1, lip=::1, TLS, session=<wCZ/0SXMnJUAAAAAAAAAAAAAAAAAAAAB>
Sep 17 02:16:17 mail dovecot[34644]: imap-login: Disconnected (no auth attempts in 21 secs): user=<>, rip=212.237.210.173, lip=212.237.210.173, TLS: read(size=580) failed: Connection reset by peer, session=<uTMK1yXMuuHU7dKt>
Sep 17 02:16:36 mail postfix/smtpd[35508]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Sep 17 02:16:37 mail postfix/smtpd[35508]: connect from localhost[::1]
Sep 17 02:16:37 mail postfix/smtpd[35508]: warning: connect to Milter service inet:127.0.0.1:11332: Connection refused
Sep 17 02:16:41 mail postfix/smtpd[35508]: warning: localhost[::1]: SASL PLAIN authentication failed:
Sep 17 02:16:49 mail postfix/smtpd[35508]: warning: localhost[::1]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Sep 17 04:21:49 mail postfix/smtpd[35508]: timeout after AUTH from localhost[::1]
Sep 17 04:21:49 mail postfix/smtpd[35508]: disconnect from localhost[::1] ehlo=1 auth=0/2 commands=1/3
Sep 17 04:23:35 mail dovecot[36551]: master: Fatal: Dovecot is already running with PID 34639 (read from /run/dovecot/master.pid)
Sep 17 04:24:20 mail postfix/smtpd[36682]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Sep 17 04:24:20 mail postfix/smtpd[36682]: connect from localhost[::1]
Sep 17 04:24:20 mail postfix/smtpd[36682]: warning: connect to Milter service inet:127.0.0.1:11332: Connection refused
Sep 17 04:24:24 mail postfix/smtpd[36682]: warning: localhost[::1]: SASL PLAIN authentication failed:
Sep 17 04:24:32 mail postfix/smtpd[36682]: warning: localhost[::1]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Sep 17 04:24:43 mail postfix/smtpd[36682]: lost connection after AUTH from localhost[::1]
Sep 17 04:24:43 mail postfix/smtpd[36682]: disconnect from localhost[::1] ehlo=1 auth=0/2 commands=1/3
Sep 17 04:28:23 mail postfix/postfix-script[37357]: fatal: the Postfix mail system is already running
Sep 17 04:28:29 mail dovecot[37383]: master: Fatal: Dovecot is already running with PID 34639 (read from /run/dovecot/master.pid)
Sep 17 04:28:35 mail postfix/smtpd[37404]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Sep 17 04:28:35 mail postfix/smtpd[37404]: connect from localhost[::1]
Sep 17 04:28:35 mail postfix/smtpd[37404]: warning: connect to Milter service inet:127.0.0.1:11332: Connection refused
Sep 17 04:28:39 mail postfix/smtpd[37404]: warning: localhost[::1]: SASL PLAIN authentication failed:
Sep 17 04:28:47 mail postfix/smtpd[37404]: warning: localhost[::1]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Sep 17 04:29:32 mail postfix/smtpd[37404]: lost connection after AUTH from localhost[::1]
Sep 17 04:29:32 mail postfix/smtpd[37404]: disconnect from localhost[::1] ehlo=1 auth=0/2 commands=1/3