Letters do not reach the recipient, how to set up STARTTLS correctly?

Question

Microsoft Exchange

I received a message that the letter was not delivered.
Delivery to the following recipients or groups is delayed:
'User' ([email protected])
Subject: RE: Member List The
message has not yet been delivered. The system will continue trying to deliver it.
The server will continue to try to deliver this message for the next 1 days, 19 hours and 50 minutes. You will be notified if the message cannot be delivered during this time.

Diagnostic information for administrators:
Forming server: mail.MAIN.COM
Receiving server: mail.CONTOSO.COM (11.11.11.11)

[email protected]
Server at mail.CONTOSO.COM (11.11.11.11) returned '400 4.4.7 Message delayed'
05/21/2020 7:36:40 AM - Server at mail.CONTOSO.COM (11/11/11) returned '451 4.4.395 Target host responded with error. -> 451 5.7.3 STARTTLS is required to send mail'

At the same time, on gmail, on mail.ru and derivatives, everything successfully leaves and is delivered in a second.
Thank you.

Answer 1

Exchange supports opportunistic TLS by default - the recipient's server may have configured Force TLS on your domain and you need a valid certificate on the send connector to your domain.

Answer 2

These are the results of the recipient server test. Maybe the problem is in the penultimate line?
We have a comodo wildcard certificate installed on the server