Fix eMail Server 451 4.3.5 Client host rejected: Server configuration error

I have a dedicated server that seems to have problems with its eMail configuration since I am no longer able to receive / send eMail. I noticed that these files are hige in size - approx 7.5 Gb each: var/log/[login to view URL] /var/log/[login to view URL] /var/log/[login to view URL] I assume the server fails to flush them and they are growing too big too fast due to the misconfiguration / errors. I'm posting some exceprts from the contents below. The server should be properly configured to be able to send and receive eMail again. You should be an expirienced server tech to solve this task. My Sever is not running Cpanel but ISP Config and is a Linux / Unix Server. I look forward to working with yoz var/log/[login to view URL] Nov 3 06:31:28 srv01 postfix/smtpd[22371]: connect from unknown[[login to view URL]] Nov 3 06:31:29 srv01 postfix/smtpd[22076]: timeout after AUTH from unknown[[login to view URL]] Nov 3 06:31:29 srv01 postfix/smtpd[22076]: disconnect from unknown[[login to view URL]] Nov 3 06:31:35 srv01 postfix/smtpd[22371]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:31:36 srv01 postfix/smtpd[22371]: disconnect from unknown[[login to view URL]] Nov 3 06:31:36 srv01 postfix/smtpd[9539]: connect from unknown[[login to view URL]] Nov 3 06:31:43 srv01 postfix/smtpd[9539]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:31:43 srv01 postfix/smtpd[9539]: disconnect from unknown[[login to view URL]] Nov 3 06:31:46 srv01 postfix/smtpd[22076]: connect from unknown[[login to view URL]] Nov 3 06:31:54 srv01 postfix/smtpd[22076]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:31:55 srv01 postfix/smtpd[22076]: lost connection after AUTH from unknown[[login to view URL]] /var/log/[login to view URL] Nov 3 06:31:35 srv01 postfix/smtpd[22371]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:31:43 srv01 postfix/smtpd[9539]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:31:54 srv01 postfix/smtpd[22076]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:32:13 srv01 postfix/smtpd[9539]: warning: connect to mysql server [login to view URL]: Access denied for user 'ispconfig'@'[login to view URL]' (using password: YES) Nov 3 06:32:13 srv01 postfix/smtpd[9539]: warning: mysql:/etc/postfix/[login to view URL]: table lookup problem Nov 3 06:32:25 srv01 postfix/smtpd[22371]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:32:45 srv01 postfix/smtpd[22076]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 Nov 3 06:33:19 srv01 postfix/smtpd[22371]: warning: connect to mysql server [login to view URL]: Access denied for user 'ispconfig'@'[login to view URL]' (using password: YES) Nov 3 06:33:19 srv01 postfix/smtpd[22371]: warning: mysql:/etc/postfix/[login to view URL]: table lookup problem Nov 3 06:33:46 srv01 postfix/smtpd[18848]: warning: unknown[[login to view URL]]: SASL LOGIN authentication failed: UGFzc3dvcmQ6 /var/log/[login to view URL] Nov 10 06:34:10 srv01 postfix/cleanup[1957]: warning: proxy:mysql:/etc/postfix/[login to view URL] lookup error for "web1@[login to view URL]" Nov 10 06:34:10 srv01 postfix/cleanup[1957]: warning: 97F1F3961231: virtual_alias_maps map lookup problem for web1@[login to view URL] -- deferring delivery Nov 10 06:34:10 srv01 postfix/error[1934]: 246993BE0CEB: to=<heiko7@[login to view URL]>, relay=none, delay=3707574, delays=3707574/0/0/0, dsn=4.4.2, status=deferred (delivery temporarily suspended: lost connection with [login to view URL][[login to view URL]] while sending DATA command) Nov 10 06:34:10 srv01 postfix/error[1934]: warning: mysql:/etc/postfix/[login to view URL]: table lookup problem Nov 10 06:34:10 srv01 postfix/error[1934]: warning: 246993BE0CEB: flush service failure