The on- offline link check is done every day.If a link can not be found in two subsequent days it will be marked as offline (red exclamation mark). On the third day an email notification will be sent to the user and the contact (website owner) - if this is defined in the corresponding settings.
An offline link will be checked for the next 14 days - therefore it can happen, that the link is online again, after the e-mail notification was sent. If the link is still offline after 14 days, it stays marked offline and will not be checked again.
Day 1: Link offline
Day 2: Link offline
Day 3: E-Mail notification sent in the morning
Day 3: Link is found again in the evening => Link will be marked as online
Day 4: Link is found => online