smtp;554 The mail could not be delivered to the recipient because the domain is not reachable. Please check the domain and try again (1479978268:301:-2147467259)

I'm receiving the following error while trying to send email to my domain. My email server remained 
down due to a technical problem yesterday, but it has been restored now. 

I'm able to send email to my domain's email addresses from yahoo, gmail etc, but I'm unable to 
send email from outlook.com to any of my email address.

I know this has happened because my mx servers remained down for few hours, but as the mx 
servers are functioning now, I'm still unable to send email to my domain's email addresses only from
 outlook.com.

Can you please look into this issue. Will this issue be resolved automatically after some time? if so, 
how long usually it takes?

Thanks


Diagnostic-Code: smtp;554 The mail could not be delivered to the recipient because the domain is not
 reachable. Please check the domain and try again (1479978268:301:-2147467259)