warning: unknown[ip]:SASL LOGIN authentication failed: authentication failure

[JasonBibby]

Seems the problem I had with a certain domain on my server hasn't gone away, they are attempting to login to the mail account and server still.

How can I stop this? I've tried blocking the IP, however they are just using multiple IP's.

Any help would be appreciated

Jan 18 10:01:32 postfix/smtpd[26946]: warning: unknown[63.141.229.83]: SASL LOGIN authentication failed: authentication failure
Jan 18 10:01:32 postfix/smtpd[26946]: lost connection after AUTH from unknown[63.141.229.83]
Jan 18 10:01:32 postfix/smtpd[26946]: disconnect from unknown[63.141.229.83]
Jan 18 10:01:32 plesk_saslauthd[27009]: activity on 1 channel(s)
Jan 18 10:01:32 plesk_saslauthd[27009]: new client (fd=10) registered
Jan 18 10:01:32 plesk_saslauthd[27009]: main cycle iteration
Jan 18 10:01:32 plesk_saslauthd[27009]: activity on 1 channel(s)
Jan 18 10:01:32 plesk_saslauthd[27009]: some read activity on client 10
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 2)=2
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=0]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 7)=7
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=1]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 2)=2
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=2]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 13)=13
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=3]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 2)=2
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=4]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 4)=4
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=5]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 2)=2
Jan 18 10:01:32 plesk_saslauthd[27009]: processing client data chunk [state=6]
Jan 18 10:01:32 plesk_saslauthd[27009]: read(10, &buf, 17)=17
Jan 18 10:01:32plesk_saslauthd[27009]: processing client data chunk [state=7]
Jan 18 10:01:32 plesk_saslauthd[27009]: No such user '' in mail authorization database