Article 5.1 of the European Copyright Directive provides that:
Temporary acts of reproduction referred to in Article 2, which are transient or incidental [and] an integral and essential part of a technological process and whose sole purpose is to enable:
(a) a transmission in a network between third parties by an intermediary, or
(b) a lawful use
of a work or other subject-matter to be made, and which have no independent economic significance, shall be exempted from the reproduction right provided for in Article 2.
The provision is designed to cover so-called incidental copying or technical copying when copyrighted materials are transmitted over the internet, in particular temporary caching and storage on servers and mail servers.