Hi Ernst, I was able to update the password on SP1 using https://<fqdn>/identity/person/passwordReminder.htm and login with new password.
However, apt-get install gluu-updater-2.4.4 shows latest SP2 package under gluu chroot /opt/upd/2.4.4.sp2 . Can you please try on SP2 and make sure to verify SMTP connection successfully.