FRITZ!Box 6490 Cable Service - Knowledge Base
Maximum number of entries in the FRITZ!Box's telephone books
Each of the local FRITZ!Box telephone books can contain up to 300 entries. Telephone books containing contacts from e-mail accounts (online telephone books) may have up to 1000 entries. However, if you have several hundred entries, it may take longer to open the user interface and navigation could be slowed down noticeably.
Note:The FRITZ!Box does not limit the number of telephone books. According to experience, it is possible to have at least 20 telephone books.