Sending to Yahoo e mail accounts from my Outlook e mail

David675 

For everyone reading this post here is the simplest way to add DKIM records, which I have found fixes the issue of sending to yahoo and aol accounts.

You will need access to whoever host your domain's DNS (for example godaddy.com)

Sign into your Office 365 tenant with an admin account https://admin.microsoft.com

Go to the Security Admin center https://security.microsoft.com

from here go to Policies & rules -> Threat Policies -> Email authentication settings

click on DKIM

Select your main domain which should bring up a new box.  ENABLE "sign messages for this domain with DKIM signatures"   Most likely you won't have DKIM records setup, so it will fail but it should give you the records you need.  They will look like this (but with your own domain):

HOST:  selector1._domainkey

TARGET: selector1-domain-com._domainkey.domain.onmicrosoft.com

HOST: selector2._domainkey

TARGET:  selector2-domain-com._domainkey.domain.onmicrosoft.com

where domain-com is your own domain (with a dash not a dot) and the end part is your "onmicrosoft.com" domain setup when you first created your 365 account.

Add these records to your DNS and then go back to Office 365 tenant and enable again.  (you may have to wait 5 - 10 minutes first)  Once enabled you are all set!

Mike