Different types of voicemail systems can typically be categorized based on the way in which recording services are provided. Some telephones, for example, include internal hardware and software that can be used to record and store messages that are left by an incoming caller. There are also systems that can be created through the use of a software program installed onto a computer, which is then connected to a phone line. Some voicemail systems are based on services offered by various companies, which allow customers to have their messages recorded, stored, and transferred automatically for different phone lines.

Some of the simplest types of voicemail systems are those that are built into a telephone or are provided through external hardware, allowing the phone itself to receive and record incoming messages. These phones can be available in a variety of different models, and can be intended for individual use or as part of a larger network. Cordless phones, for example, can be used with a base model or a separate device that receives and records messages, which can then be accessed either directly or through an access code dialed into a handset. This allows a series of handsets to be used as part of a larger network, which can all access the voicemail systems to which they are connected.

Other voicemail systems can be created through the use of software that allows a computer to function as part of a telephone network. Once this program is installed, and the computer is connected to a phone line, then incoming calls can be routed to the program on the computer. This allows missed calls to be received by the software, which then provides the caller with an opportunity to leave a message. These kinds of voicemail systems can then store recorded messages as audio computer files, which can be sent to the owner of the system via email or as a message to a mobile phone.

There are also a number of voicemail systems that can be provided by various third-party companies and services. Many phone service providers, for example, also offer voicemail recording for clients who have a phone number through the service. There are also companies that do not offer telephone service, but which can be used to set up voicemail systems on different types of phone lines. Once an incoming call is missed, then it is transferred to the third-party system that records the message and can then be accessed externally by the client through an access code and password.