Muchos log con authentication failure

[epick]

Hola,

Echando un vistazo a los log me he encontrado con lo siguiente, creo q algunos clientes de correo están tratando de autenticarse de otras formas sin tener éxito, como hago para que no se generen estos tipos de log ya que tengo un IDS monitoreando los log y cada 10min me llega este tipo de correo.

Agradeceré su pronta ayuda, saludos

Aquí dejo los log

Jun 9 11:04:03 hosting postfix/smtpd[30023]: warning: unknown[190.33.245.195]: SASL NTLM authentication failed: authentication failure
Jun 9 11:03:56 hosting postfix/smtpd[30027]: warning: unknown[190.33.245.195]: SASL DIGEST-MD5 authentication failed: authentication failure
Jun 9 11:03:56 hosting postfix/smtpd[30027]: warning: unknown[190.33.245.195]: SASL NTLM authentication failed: authentication failure
Jun 9 11:03:56 hosting postfix/smtpd[30027]: warning: unknown[190.33.245.195]: SASL DIGEST-MD5 authentication failed: authentication failure
Jun 9 11:03:56 hosting postfix/smtpd[30027]: warning: unknown[190.33.245.195]: SASL NTLM authentication failed: authentication failure
Jun 9 11:03:17 hosting postfix/smtpd[30023]: warning: unknown[190.33.245.195]: SASL DIGEST-MD5 authentication failed: authentication failure
Jun 9 11:03:17 hosting postfix/smtpd[30023]: warning: unknown[190.33.245.195]: SASL DIGEST-MD5 authentication failed: authentication failure
Jun 9 11:03:16 hosting postfix/smtpd[30023]: warning: unknown[190.33.245.195]: SASL NTLM authentication failed: authentication failure