Classification Rejected

Reason

Definition

450 4.1.1

Rejection when relay check is enabled

450 4.1.8

DNS error of sender domain (temporarily blocked)

450 4.5.5

Early spam detection (temporarily blocked)

450 4.5.6

Temporary internal failure

450 4.5.7

Temporary internal failure

504 5.5.2

Error in sender address according to RFC

504 5.5.2

Error in recipient address according to RFC

550 5.1.1

Unknown recipient (SMTP check)

550 5.2.2

Explicit blocking of sender or recipient address

550 5.5.3

Multi-recipient bounce email

552 5.5.2

Message size (Content Control)

554 5.5.3

Content Filter (email size, outgoing)

554 5.5.4

IP sender address with a negative reputation

554 5.5.5

Spam detection (outgoing)

554 5.5.6

Loop detected

554 5.5.7

Content Filter (attachment, outgoing)

554 5.6.1

signature of mass spam in mail header or subject

554 5.6.2

signature of mass spam links detected

554 5.6.3

signature of mass spam in text detected

554 5.6.4

Virus email blocked

554 5.6.5

TLS encryption required by customer rule

554 5.7.1

Unknown domain or unknown recipient (LDAP check)