"FREEMAIL_FORGED_REPLYTO" issue

Tags: #<Tag:0x00007effff1fa288>

Hi
I made a test with mail-tester.com to check the score of the emails sent by phplist.
The score is good, 7.7.
The main and only issue is the FREEMAIL_FORGED_REPLYTO:
“-2.503 FREEMAIL_FORGED_REPLYTO Freemail in Reply-To, but not From”
What should I check/fix?
thanks for any help