A domain will be deactivated, when the e-mail address, that has been entered for the domain owner, was not successfully validated. As a result, the website incl. the connected services will be inaccessible.
As far as a domain contact is necessary for registration, the domain owner has 15 days to validate the e-mail address. If there was no validation within 15 days, the domain will be deactivated.
As part of the ICANN Registrar Accreditation Agreement 2013 an e-mail verification of the domain owners became necessary for all already registered and future generic TLDs (e.g. .COM, .NET, .ORG, .INFO) and sponsored TLDs (e.g. .TEL, .MOBI, .ASIA).
This guideline is set by the registry and exists for all registrars.