Fix EXIM Error : all hosts for ‘domain.tld’ have been failing for a long time (and retry time not reached)

An error encountered on Private email servers, when trying to send to the e-mail addresses from a particular field or on a specific e-mail address.
The scenario is as simple as possible.
We have a private e-mail address (ie Gmail, MSN, Outlook, ICLOUD, YAHOO!, Etc) we cannot send messages to another private e-mail address. The returned message will be this:

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
mail_destinatar@domain.tld
all hosts for ‘domain.tld’ have been failing for a long time (and retry time not reached)

In most situations this error appears when database “Exim Retry"It is corruption. So the problem is on Sever from which you try to ship the message.

Solving the error consists of Delete Exim Retry Database and Restarting the Exim Service pe server.

Execute the following command lines in the server to delete the Exim Vey database:

cd /var/spool/exim/db
rm -f retry retry.lockfile
rm -f wait-remote_smtp wait-remote_smtp.lockfile

After the execution of these commands through which the fields will be deleted: Retry, Retry.Lockfile, Wait-Remote_SMTP and Wait-Remote_SMTP.Lockfile, restart the "Exim" service.

service exim restart

For the execution of these orders you must have access to the server console (or SSH access) and sufficient permissions.