Upgrade 7 to 8 i am in stopping email in out.

PROBLEM RESOLVED

Hi

I have upgraded my dollibar 7 to dollibar 8.
Upgrade is ok and no problem.
now i have problem com email in out .
new request in setup email are:

MAIN_MAIL_EMAIL_DKIM_ENABLED Sì
MAIN_MAIL_EMAIL_DKIM_DOMAIN
MAIN_MAIL_EMAIL_DKIM_SELECTOR
MAIN_MAIL_EMAIL_DKIM_PRIVATE_KEY

Parse error: syntax error, unexpected ‘?’ in C:\dolibarr\www\dolibarr\htdocs\includes\swiftmailer\lib\classes\Swift\Mime\SimpleMessage.php on line 496

what i must put in this request ?
URGENT i am in stopping email in out.

Thank you for your help

Roberto