TYPO3 Core

Hi,
We have a smtp mail problem since december, it makes me mad..
in V9.5 and even V10, at the beginning, we sent mails via smtp and port 587, via starttls as I presume.
'transport_smtp_encrypt' => 'tls',//later we tried false, also not working;
error:

Failed to find an authenticator supported by the SMTP server

we switched back to sendmail. but we want smtp.
we try again:
I found out that during the outlook-Problems end 202 security on the outlook-Server had been improved,
the mail-host and the webspace host are both sure they support TLSv1.2, but the webspace hoster told me to switch to port 465 on which they would normaly deliver TLSv1.2 and not STARTTLS like on port 587. (->failed to find authenticator..)

So I tried port 465, but then we get the other error:

Connection could not be established with host "ssl://exchange.mydomain.de:465": stream_socket_client(): unable to connect to ssl://exchange.mydomain.de:465 (Connection timed out)

'transport_smtp_encrypt' true or false doesn't matter, it's always ssl.
and there is the problem: our exchange-server doesn't support ssl. https or smtp or some others would work..
is there a chance to configure the protocol?
with the best regards,
Sabine