Anonymous - 2012-04-18

Hi. I am working with a webmin account . I enter Postfix mail configurations and its so fuzzy . I cand  make out what to do in order to send emails . When I send emails they are added to queue . And in the queue section I see this error
"425 bytes SASL authentication failed; server smtp.sendgrid.net said: 535 Authentication failed: Bad username / password" or"563 bytes mail transport unavailable" .
Could you help me with this ?