1. A method for electronic mail message processing, comprising: obtaining a set of keywords associated with an electronic mail message; updating, using one or more computer processors and based at least in part on the set of keywords, a set of inverted index records stored in a level 1 cache; determining whether size of the set of inverted index records stored in the level 1 cache exceeds a first preset threshold value; in the event that the first preset threshold value is exceeded, transferring the set of inverted index records in the level 1 cache to a level 2 cache; determining whether size of a level 2 cache file exceeds a second preset threshold value; and in the event that the second preset threshold value is exceeded, transferring, according to a path file, inverted index records in the level 2 cache file to a level 3 cache storing a set of inverted index files; wherein the path file stores mapping relationship information of the keywords and corresponding level 3 inverted index files.