DKIM, SPF record settings

I have a problem with outgoing mail on our server. When sending messages to @gmail.com addresses, returns are coming in:

host gmail-smtp-in.l.google.com[142.251.168.27] said:

550-5.7.26 Your email has been blocked because the sender is

unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with

either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results:

550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [*] with ip:

[46.105.40.13] = did not pass 550-5.7.26 550-5.7.26 For instructions on

setting up authentication, go to 550 5.7.26

https://support.google.com/mail/answer/81126#authentication

ffacd0b85a97d-37ecf13946fsi563525f8f.861 - gsmtp (in reply to end of DATA

command)

We use Hosted Exchange at OVH where we have a domain added. Our server, in turn, is served by DirectAdmin. Please report from people with experience in the topic :-)