Alice.it and Tim.it bounce email messages from amazon SES

Hi all, in the last two days we have noticed that that the italian domain tim.it and alice.it bounces all the email from our account. We also have tried using a dedicated IP but the problem persist. Here the error we receive every time

{"notificationType":"Bounce","bounce":{"feedbackId":"0113018ae07b9841-85cd5ccf-7426-4d1e-bde2-5fcf5b07cb58-000000","bounceType":"Transient","bounceSubType":"General","bouncedRecipients":[{"emailAddress":"xxxxxxx@tim.it","action":"failed","status":"5.3.0","diagnosticCode":"smtp; 550 mail not accepted from blacklisted IP address [23.251.247.100]"}],"timestamp":"2023-09-29T10:28:30.000Z","remoteMtaIp":"34.141.161.132","reportingMTA":"dns; e246-9.smtp-out.eu-west-3.amazonses.com"},"mail":{"timestamp":"2023-09-29T10:28:29.527Z","source":"xxxxx@xxxxxx.xx","sourceArn":"arn:aws:ses:eu-west-3:xxxxxxxxxxxxxxxxxxxxx","sourceIp":"xxxxxxxxxx","callerIdentity":"root","sendingAccountId":"xxxxxxxxxxxxxxxxxxx","messageId":"0113018ae07b92d7-0c4bdedd-38da-4cf9-a480-8639e7242479-000000","destination":["xxxxxxxxxx@tim.it"],"headersTruncated":false,"headers":[{"name":"From","value":"xxxxxxxx@xxxxx.xx"},{"name":"To","value":"xxxxxxx@tim.it"},{"name":"Subject","value":"Prova AWS"},{"name":"MIME-Version","value":"1.0"},{"name":"Content-Type","value":"multipart/alternative; boundary="----=_Part_146504_123947408.1695983309531""}],"commonHeaders":{"from":["xxxxxx@xxxxxx.xx"],"to":["xxxxxxx@tim.it"],"subject":"Prova AWS"}}}

regards