not receiving mails from a specific domain name

not receiving mails from a specific domain name

Dear support staff,

I have already emailed you about this issue but since there is no reply, I want to try this forum. from last week my email address b""""""@tjay.com is not receiving emails only from irco.com. there are no emails in spam folder as well. all the other email addresses in tjay.lk domain name are receiving emails from irco.com but b"""""" @tjay.lk . I'm using the admin account of tjay.lk and spam filtering is also turned off and irco.com has been added to the white list for a longer period of a time. please check and troubleshoot as soon as possible since I'm the corresponding contact for one our major products. Me one my contact both are using outlook.
And attached  is the error message that they receive. Last time I have received an email from irco.com on 13th.