I’ve heard the anacronym “DKIM” in conversation about 10 times just in the past week so I’m putting some resources up here for you to setup DKIM yourself.
Total Uptime has instructions that provide some good background information on all of the steps involved in deploying DKIM. You can find those instructions at https://totaluptime.com/kb/how-do-i-create-a-dkim-domain-key-record/
DMARCLY has a DKIM generator available at https://dmarcly.com/tools/dkim-record-generator
POWEREDMARC has a DKIM generator available at: https://powerdmarc.com/dkim-record-generator/
EASYDMARC has a DKIM generator available at https://easydmarc.com/tools/dkim-record-generator/
The generator I most recently used was EASYDMARC’s.
EASYDMARC also has a DKIM Checker and Lookup tool available at https://easydmarc.com/tools/dkim-lookup
If your email is hosted in the Microsoft 365 cloud you still should setup DKIM for your domain. Instructions to setup DKIM for your domain can be found at https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/email-authentication-dkim-configure?view=o365-worldwide
You can go to Wikipedia for more background information on DKIM at https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail