When i try to send mail messages the panel give me this error 
I am using digital ocean server with all ports open (in especific the 25 port)
console:
Jul 11 18:01:10 rihosting sendmail[53004]: My unqualified host name (rihosting) unknown; sleeping for retry
Jul 11 18:02:10 rihosting sendmail[53004]: unable to qualify my own domain name (rihosting) -- using short name
Jul 11 18:02:10 rihosting sendmail[53004]: alias database /etc/mail/aliases rebuilt by root
Jul 11 18:02:10 rihosting sendmail[53004]: /etc/mail/aliases: 0 aliases, longest 0 bytes, 0 bytes total
Jul 11 18:02:11 rihosting sm-mta[71599]: My unqualified host name (rihosting) unknown; sleeping for retry
Jul 11 18:02:13 rihosting sm-msp-queue[72846]: My unqualified host name (rihosting) unknown; sleeping for retry
Jul 11 18:03:11 rihosting sm-mta[71599]: unable to qualify my own domain name (rihosting) -- using short name
Jul 11 18:03:11 rihosting sm-mta[96081]: starting daemon (8.15.2): SMTP+queueing@00:10:00
Jul 11 18:03:13 rihosting sm-msp-queue[72846]: unable to qualify my own domain name (rihosting) -- using short name
Jul 11 18:19:22 rihosting postfix/postfix-script[335016]: starting the Postfix mail system
Jul 11 18:19:22 rihosting postfix/master[335018]: daemon started -- version 3.6.4, configuration /etc/postfix
Jul 11 18:20:10 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up without any protocols (core dumps disabled)
Jul 11 18:20:13 rihosting dovecot: master: Warning: Killed with signal 15 (by pid=339286 uid=0 code=kill)
Jul 11 18:20:15 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up for imap, lmtp, pop3 (core dumps disabled)
Jul 11 22:33:09 rihosting postfix/postfix-script[357326]: stopping the Postfix mail system
Jul 11 22:33:09 rihosting postfix/master[335018]: terminating on signal 15
Jul 11 22:33:10 rihosting postfix/postfix-script[357565]: starting the Postfix mail system
Jul 11 22:33:10 rihosting postfix/master[357567]: daemon started -- version 3.6.4, configuration /etc/postfix
Jul 11 22:33:13 rihosting dovecot: master: Warning: Killed with signal 15 (by pid=357694 uid=0 code=kill)
Jul 11 22:33:14 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up for imap, pop3, lmtp (core dumps disabled)
Jul 11 22:33:17 rihosting dovecot: master: Warning: Killed with signal 15 (by pid=357736 uid=0 code=kill)
Jul 11 22:33:17 rihosting postfix/postfix-script[357745]: stopping the Postfix mail system
Jul 11 22:33:17 rihosting postfix/master[357567]: terminating on signal 15
Jul 11 22:33:17 rihosting postfix/postfix-script[357984]: starting the Postfix mail system
Jul 11 22:33:17 rihosting postfix/master[357986]: daemon started -- version 3.6.4, configuration /etc/postfix
Jul 11 22:33:18 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up for imap, pop3, lmtp (core dumps disabled)
Jul 11 22:35:09 rihosting dovecot: pop3-login: Disconnected: Connection closed: SSL_accept() failed: error:0A000076:SSL routines::no suitable signature algorithm (no auth attempts in 0 secs): user=<>, rip=172.104.14.62, lip=134.122.120.139, TLS handshaking: SSL_accept() failed: error:0A000076:SSL routines::no suitable signature algorithm, session=<LboWKo/jSO6saA4+>
Jul 11 22:36:05 rihosting dovecot: master: Warning: Killed with signal 15 (by pid=358117 uid=0 code=kill)
Jul 11 22:36:07 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up for imap, pop3, lmtp (core dumps disabled)
Jul 11 22:36:07 rihosting dovecot: config: Warning: /etc/dovecot/conf.d/10-ssl.conf line 20: Global setting ssl_cert won't change the setting inside an earlier filter at /etc/dovecot/conf.d/10-ssl.conf line 11 (if this is intentional, avoid this warning by moving the global setting before /etc/dovecot/conf.d/10-ssl.conf line 11)
Jul 11 22:36:07 rihosting dovecot: config: Warning: /etc/dovecot/conf.d/10-ssl.conf line 21: Global setting ssl_key won't change the setting inside an earlier filter at /etc/dovecot/conf.d/10-ssl.conf line 12 (if this is intentional, avoid this warning by moving the global setting before /etc/dovecot/conf.d/10-ssl.conf line 12)
Jul 11 22:42:07 rihosting dovecot: imap-login: Login: user=<suporte@rihosting.xyz>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=358399, secured, session=<pfcCQ4/jQph/AAAB>
Jul 11 22:42:07 rihosting dovecot: imap(suporte@rihosting.xyz)<358399><pfcCQ4/jQph/AAAB>: Disconnected: Connection closed (CLOSE finished 0.001 secs ago) in=73 out=1482 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Jul 11 22:42:36 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<t869RI/japl/AAAB>
Jul 11 22:42:36 rihosting postfix/submission/smtpd[358404]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Jul 11 22:42:36 rihosting postfix/smtpd[358408]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Jul 11 22:42:36 rihosting dovecot: imap-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<8d+9RI/jRJh/AAAB>
Jul 11 22:42:36 rihosting postfix/smtps/smtpd[358407]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Jul 11 22:42:36 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<3QC+RI/j/pR/AAAB>
Jul 11 22:42:36 rihosting dovecot: imap-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<iB2+RI/jMIJ/AAAB>
Jul 11 22:42:36 rihosting postfix/smtps/smtpd[358407]: warning: error opening chain file: /etc/ssl/private/ssl-cert-snakeoil.key: No such file or directory
Jul 11 22:42:36 rihosting postfix/submission/smtpd[358404]: warning: error opening chain file: /etc/ssl/private/ssl-cert-snakeoil.key: No such file or directory
Jul 11 22:42:36 rihosting postfix/smtps/smtpd[358407]: connect from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/smtpd[358408]: warning: error opening chain file: /etc/ssl/private/ssl-cert-snakeoil.key: No such file or directory
Jul 11 22:42:36 rihosting postfix/submission/smtpd[358404]: connect from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/smtps/smtpd[358407]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/smtps/smtpd[358407]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:36 rihosting postfix/submission/smtpd[358404]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/submission/smtpd[358404]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:36 rihosting postfix/smtpd[358408]: connect from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/smtpd[358408]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:36 rihosting postfix/smtpd[358408]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:48 rihosting postfix/submission/smtpd[358404]: connect from localhost[127.0.0.1]
Jul 11 22:42:48 rihosting postfix/submission/smtpd[358404]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:48 rihosting postfix/submission/smtpd[358404]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:48 rihosting postfix/smtps/smtpd[358407]: connect from localhost[127.0.0.1]
Jul 11 22:42:48 rihosting postfix/smtps/smtpd[358407]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:48 rihosting postfix/smtps/smtpd[358407]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:48 rihosting dovecot: imap-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<huV4RY/jRph/AAAB>
Jul 11 22:42:48 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<YvB4RY/jbJl/AAAB>
Jul 11 22:42:48 rihosting dovecot: imap-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<tRh5RY/jMoJ/AAAB>
Jul 11 22:42:48 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<ey95RY/jAJV/AAAB>
Jul 11 22:42:55 rihosting postfix/smtpd[358408]: connect from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/submission/smtpd[358404]: connect from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/submission/smtpd[358404]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/submission/smtpd[358404]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:55 rihosting postfix/smtpd[358408]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/smtpd[358408]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:55 rihosting postfix/smtps/smtpd[358407]: connect from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/smtps/smtpd[358407]: lost connection after CONNECT from localhost[127.0.0.1]
Jul 11 22:42:55 rihosting postfix/smtps/smtpd[358407]: disconnect from localhost[127.0.0.1] commands=0/0
Jul 11 22:42:55 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<WXniRY/jbpl/AAAB>
Jul 11 22:42:55 rihosting dovecot: imap-login: Disconnected: Connection closed (disconnected before auth was ready, waited 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<DXXiRY/jSJh/AAAB>
Jul 11 22:42:55 rihosting dovecot: imap-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<Eb7iRY/jNIJ/AAAB>
Jul 11 22:42:55 rihosting dovecot: pop3-login: Disconnected: Connection closed (no auth attempts in 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: Connection closed, session=<IMXiRY/jApV/AAAB>
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: error: open database /etc/postfix/vmail_ssl.map.db: No such file or directory
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: warning: error opening chain file: /etc/ssl/private/ssl-cert-snakeoil.key: No such file or directory
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: connect from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: lost connection after UNKNOWN from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: disconnect from scanner-07.ch1.censys-scanner.com[167.94.138.61] unknown=0/1 commands=0/1
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: connect from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: lost connection after CONNECT from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: disconnect from scanner-07.ch1.censys-scanner.com[167.94.138.61] commands=0/0
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: connect from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: SSL_accept error from scanner-07.ch1.censys-scanner.com[167.94.138.61]: -1
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: warning: TLS library problem: error:0A000076:SSL routines::no suitable signature algorithm:../ssl/t1_lib.c:3220:
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: lost connection after STARTTLS from scanner-07.ch1.censys-scanner.com[167.94.138.61]
Jul 11 22:48:26 rihosting postfix/smtps/smtpd[359570]: disconnect from scanner-07.ch1.censys-scanner.com[167.94.138.61] ehlo=1 starttls=0/1 commands=1/2
Jul 11 22:51:46 rihosting postfix/anvil[359572]: statistics: max connection rate 3/60s for (smtps:167.94.138.61) at Jul 11 22:48:26
Jul 11 22:51:46 rihosting postfix/anvil[359572]: statistics: max connection count 1 for (smtps:167.94.138.61) at Jul 11 22:48:26
Jul 11 22:51:46 rihosting postfix/anvil[359572]: statistics: max cache size 1 at Jul 11 22:48:26
Jul 11 22:54:01 rihosting dovecot: master: Warning: Killed with signal 15 (by pid=359655 uid=0 code=kill)
Jul 11 22:54:02 rihosting dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up for imap, pop3, lmtp (core dumps disabled)
Jul 11 22:54:02 rihosting postfix/postfix-script[359675]: stopping the Postfix mail system
Jul 11 22:54:02 rihosting postfix/master[357986]: terminating on signal 15
Jul 11 22:54:03 rihosting postfix/postfix-script[359914]: starting the Postfix mail system
Jul 11 22:54:03 rihosting postfix/master[359916]: daemon started -- version 3.6.4, configuration /etc/postfix
