This is the mail system at host mail.dervish.ru.
 
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                   The mail system
 
<serg@dervish.ru>: temporary failure. Command output: doveconf: Fatal: Error in
    configuration file /etc/dovecot/conf.d/10-ssl.conf line 29: ssl_ca: Can't
    open file /etc/letsencrypt/live/dervish.ru/chain.pem: Permission denied
 
Если в нем есть какая-то для вас польза)