Mystery of the Eircom phantoms

How many have noticed that in the quiet hours of night/early morning their Eircom email accounts become unavailable?
And that is on a regular daily, or nightly as it is, occurrence.

Connection attempts from email clients produce the bizarre error message 'log in details or password incorrect' - bizarre given that those very same details consistently work when the mail service is running as it should. Trying to access via webmail produces a page cannot be found error message.

Attempts to seek an answer from Eircom failed altogether. Emails were not answered.

There are probably many folk with a free eircom.net email account - obtainable to those who have an Eircom phone line.
There are also probably many who no longer have an Eircom line or broadband service but who still use their eircom.net email account.

Support services are not available to those without an Eircom account.

So, the question remains - why is the email service so intermittent overnight?

Is this perhaps a convenient time to crawl and file the data?