Outbound email marked as spam somewhere in the path

#1

i attempted to email an @yahoo.com account received the following:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

    [*****@yahoo.com](mailto:******@yahoo.com)
    host filtergroup.mxroute.com [149.28.56.236]
    SMTP error from remote mail server after end of data:
    554 5.7.1 Outbound spam message rejected

    Reporting-MTA: dns; blizzard.mxrouting.net

    Action: failed
    Final-Recipient: rfc822;[********@yahoo.com](mailto:******@yahoo.com)
    Status: 5.0.0
    Remote-MTA: dns; filtergroup.mxroute.com
    Diagnostic-Code: smtp; 554 5.7.1 Outbound spam message rejected

Then I attempted to send the same message to support@mxroute.com and received the same error. It appears that my outbound emails are being viewed as spam.

his message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[support@mxroute.com](mailto:support@mxroute.com)
host filtergroup.mxroute.com [149.28.56.236]
SMTP error from remote mail server after end of data:
554 5.7.1 Outbound spam message rejected

Reporting-MTA: dns; blizzard.mxrouting.net

Action: failed
Final-Recipient: rfc822;[support@mxroute.com](mailto:support@mxroute.com)
Status: 5.0.0
Remote-MTA: dns; filtergroup.mxroute.com
Diagnostic-Code: smtp; 554 5.7.1 Outbound spam message rejected
#2

We’ve recently identified a trend from compromised email accounts (mostly referring to users who reused passwords and were compromised elsewhere) that we have been unable to capture except by enforcing a new rule in the filters. The rule is that outbound email will be rejected which matches this:

“Has text part encoded in base64 that does not contain any 8bit characters”

This is used to conceal content behind encoding to confuse spam filters. We’re not seeing widespread use of this for any other purpose, and our position is that it’s a bit odd to use it to conceal plain text as it does not add any security or function to the email. You’ve been whitelisted for now.