One-click unsubscribe no longer working with Apple Mail.

[thelittlerocket]

It was working without problem, but recently I noticed that I still got emails from the sender who I already clicked the unsubscribe, checking the admin panel, the contact was not been deactivated, and from log, fund following info

Apr 30 17:12:31 hostname postfix/smtp[2697]: C794C206C1: to=<simplelogin-unsubscriber@mydomain.com>, relay=127.0.0.1[127.0.0.1]:20381, delay=0.32, delays=0.3/0/0.01/0.01, dsn=5.0.0, status=bounced (host 127.0.0.1[127.0.0.1] said: 550 SL E507 Wrongly formatted subject (in reply to end of DATA command))
Apr 30 18:01:06 hostname postfix/smtp[29240]: B6945206B6: to=<simplelogin-unsubscriber@mydomain.com>, relay=127.0.0.1[127.0.0.1]:20381, delay=0.65, delays=0.61/0.02/0/0.01, dsn=5.0.0, status=bounced (host 127.0.0.1[127.0.0.1] said: 550 SL E507 Wrongly formatted subject (in reply to end of DATA command))
Apr 30 18:01:48 hostname postfix/smtp[29240]: 1B1B9206B6: to=<simplelogin-unsubscriber@mydomain.com>, relay=127.0.0.1[127.0.0.1]:20381, delay=0.32, delays=0.3/0/0/0.01, dsn=5.0.0, status=bounced (host 127.0.0.1[127.0.0.1] said: 550 SL E507 Wrongly formatted subject (in reply to end of DATA command))
Apr 30 18:08:02 hostname postfix/smtp[32239]: 942FB206B6: to=<simplelogin-unsubscriber@mydomain.com>, relay=127.0.0.1[127.0.0.1]:20381, delay=0.65, delays=0.62/0.01/0/0.01, dsn=5.0.0, status=bounced (host 127.0.0.1[127.0.0.1] said: 550 SL E507 Wrongly formatted subject (in reply to end of DATA command))
Apr 30 18:11:31 hostname postfix/smtp[980]: 9ACF629A32: to=<simplelogin-unsubscriber@mydomain.com>, relay=127.0.0.1[127.0.0.1]:20381, delay=0.61, delays=0.58/0.01/0/0.01, dsn=5.0.0, status=bounced (host 127.0.0.1[127.0.0.1] said: 550 SL E507 Wrongly formatted subject (in reply to end of DATA command))

Has anyone encountered this before?
Any help would be appreciated.

MacOS: 14.4.1 (23E224)
Apple Mail: Version 16.0 (3774.500.171.1.1)
Simple-long: 4.42.2