Error: 554 Message Not Allowed

[BrotherAndrew]

PHP Sending was Turned Off, and Now I'm Using smtp@DefaultDomainName.*** when Sending Email from Various Domain Names.  And Yahoo is Giving a 554 Message Not Allowed Error,  Simply from Replying to an Email that a Sister Sent to one of my Brothers & I.  Is it Possible that Yahoo Sees 2 Different Domain Names in the Header, and Thinks It's Fishy?   

[BrotherAndrew]

I Tested a Few Hours ago, and that Issue Hasn't gone away yet.