The Services menu holds the functions that the PBX offers on top of plain calls: e-mail delivery for voicemail and missed calls, the voicemail system itself, conference rooms and your own audio files such as music on hold.
Most changes here are stored first and become active after you apply them, see Applying changes.
Notifications
The outgoing mail server (SMTP) for voicemail and missed call e-mails, and a test message.
Voicemail
Voicemail-to-e-mail, missed call e-mails and their texts per language.
Conferencing
Conference rooms with optional PIN and admin PIN, reachable internally and from outside.
Media
Music on hold, the voicemail greeting, IVR announcements, recording by phone, text to speech and the prompt language.