Resolve issue with "This message does not pass authentication checks (SPF and DKIM)

Job ID: 35853093

Budget: €8 – €30 EUR

I have been trying to resolve an issue with emails being guided to spam boxes due to the error:
This message does not pass authentication checks (SPF and DKIM)
Who can help in resolving this issue?
I need advise and can give you access if necessary.
Using Ubuntu server SMTP server.
What is your billing for this?
Related categories: System Admin Linux Ubuntu SMTP