Hello all,

Since yesterday my zoho mailbox connected to a valid and owned domain has been neither able to send nor receive e-mails citing the reason as follows:

This message was created automatically by mail delivery system.  THIS IS A WARNING MESSAGE ONLY.  YOU DO NOT NEED TO RESEND YOUR MESSAGE.  The original message was received at Fri, 22 Feb 2019 05:31:08 -0800  from [my e-mail] ----- The following addresses had fatal errors -----  [Status: ERROR, Address: <recipient 1 @ valid domain>, ResponseCode 450, 4.1.8 <my e-mail>: Sender address rejected: Domain not found, Status: ERROR, Address: <recipient 2@ valid domain>, ResponseCode 450, 4.1.8 <my e-mail>: Sender address rejected: Domain not found, Status: ERROR, Address: <recipient 3@ valid domain>, ResponseCode 450, 4.1.8 <my e-mail>: Sender address rejected: Domain not found, Status: ERROR, Address: <recipient 4@ valid domain>, ResponseCode 450, 4.1.8 <my e-mail>: Sender address rejected: Domain not found]  Message will be retried for 4 more day(s)

I must add that the recipient e-mails have had no issue receiving e-mails from my mailbox in the past and from other contacts in the present.

Not exactly sure what is causing the issue or how to resolve it.
Any help would be much appreciated.

Kind regards,

V