There is a weird problem that I cannot think of any solution. There is a mail server Xs that has couple of domains on it and it is in Datacenter Xd. And there is a mail server Ys that has couple od domains also in another Datacenter Yd.
For only 1 domain and 1 user account the mail dont come. For instance;
alice(at)domain(in)Yd.com but cannot send hardy(at)domain(in)Yd.com
we tried numerous things and at last we deleted the accounts and created them again, but problem still exists.
What do you think has happened to these accounts ?