Mail delivery failed: returning message to sender

[Mail Delivery System]

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:

  gdb@sourceware.org
    host sourceware.org [8.43.85.97]
    SMTP error from remote mail server after end of data:
    550 5.7.1 Blocked by SpamAssassin