mailto:emailaccountuntergmail@gmail.com: host gmail-smtp-in.l.google.com[123.123.123.123] said:
    550-5.7.26 This mail is unauthenticated, which poses a security risk to the
    550-5.7.26 sender and Gmail users, and has been blocked. The sender must
    550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
    550-5.7.26 DKIM checks did not pass and SPF check for
    [kleintierhof-rauris.at] 550-5.7.26 did not pass with ip: [83.246.86.183].
    The sender should visit 550-5.7.26
    https://support.google.com/mail/answer/81126#authentication for 550 5.7.26
    instructions on setting up authentication.
    z8-20020adfd0c8000000b0030fb4dc66bbsi428380wrh.144 - gsmtp (in reply to end
    of DATA command)