Sending email authless

Is it possible to send email from Gitea using Exchange without auth? Docs didn’t help me with that.
Gitea gives me this error:

gomail: could not send email 1: Mail: 530 5.7.1 Client was not authenticated

If I understand this correctly this is not determined on the Gitea side but on the side of your Exchange server. We send authless email from our gitea instance to an accepting relay within our company. All it needs to know is that the IP we are relaying from is in the authorized list of relay IPs. No username or password required. The only thing you’d have to worry about is if you are using SMTPS with TLS, then you have to ensure the TLS connection is properly happening. We do ours with port 25 since it’s all internal and controlled by the allowed networks (IPs).