Email was re-sent once for now.

It seems that en email scheduled to be sent at x, when the cron runs after it, appears this message Email was re-sent once for now. and the email .

At the same time that specific email is sent twice.

The receiver gets tow emails.

How can it be disabled?

Why the software resend the email that, at the point of cron execution is not sent, but it resends it.

It seems that en email scheduled to be sent at x, when the cron runs after it, appears this message Email was re-sent once for now. and the email .
At the same time that specific email is sent twice.
The receiver gets tow emails.
How can it be disabled?
Why the software resend the email that, at the point of cron execution is not sent, but it resends it.