client notifications not geting to clients

[Iu Donadeu]

hi, since 21 of October, noone of our notifications are being recived, no configurations have been touched before, i made sure all notifications are enabled, he following error apears at the registry of the notifications, checked with our domain probider, and they confirmed they are not blocking anything related to jira: 

Error del proveedor de correo electrónico: 554 5.4.7 [internal] message timeout (exceeded max time, last transfail: 421 4.4.0 [internal] no mail servers for this domain could be reached at this time)

in the help options its says that internal errors happen within Jira and shuld be fixing itself, but this have been going for weeks now.

Have tested it with a brand new account as a client, so i can guarantee no client side configurations afecting, this is happening to all our  clients, they all have the same domain. Have tried from an acount made with a google.com domain and its geting the notifications right, so feels like clients notifications to our domain are blocked internally in jira for some reason.

funny enough the administratos have the same domain aswell and they get the internal notifications, still if they make a tickets as a client, they are not geting the ticket updates notification aswell....