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Phplist: Send mail ok. SpamAssassin: RCVD_DOUBLE_IP_SPAM

Hello.
I have a problem with SpamAssassin. When I send a test email to mail-tester.com to check the result, I always get the error: RCVD_DOUBLE_IP_SPAM Bulk email fingerprint (double IP) found.
However, when I send an e-mail via a regular e-mail program, this error is not present. Is something wrongly positioned? I am asking you to direct what the problem is. Thank you in advance for your help.