Emails to a regular contact have not been received in recent weeks. Looking into the problem, we learned that Spam detection software, running on the system “mxin018.mail.hostpoint.ch”,
has identified this incoming email as possible spam. … Also:

0.0 FREEMAIL_FROM          Sender email is commonly abused enduser mail
                           provider
                           [barmur[at]sunrise.ch]
0.0 HTML_MESSAGE           BODY: HTML included in message
0.1 DKIM_SIGNED            Message has a DKIM or DK signature, not necessarily
                           valid
-0.1 DKIM_VALID             Message has at least one valid DKIM or DK signature
-0.1 DKIM_VALID_AU          Message has a valid DKIM or DK signature from
                           author’s domain
-0.1 DKIM_VALID_EF          Message has a valid DKIM or DK signature from
                           envelope-from domain
-0.8 DCC_REPUT_00_12        DCC reputation between 0 and 12 % (mostly ham)

The original message was not completely plain text, and may be unsafe to
open with some email clients; in particular, it may contain a virus,
or confirm that your address can receive spam.

Has anyone else had this problem?If so, how did you solve the issues?