A monotone voice can be a turn off for a caller. You want your caller to feel like they missed out on speaking with you — not like they dodged a bullet.
If you only check and return messages once a day or once a week, let your caller know. This will avoid multiple messages by the same caller.

Cox is providing access to the new voice mail platform seven (7) days before the migration to pre-initialize your new mailbox. This allows you to log in and change your PIN, record your name, implement preferred settings, familiar yourself with the new key presses, verify distribution lists and record other greetings. See the Quick Reference Guide for instructions.
Users often don’t invest enough time into their messages, resulting in incomplete, unprofessional, or otherwise under-whelming greetings. Sure, crafting a greeting doesn’t sound all that complicated; however, there are a number of pitfalls users can fall into—i.e. informality, terseness, sincerity, lack of direction, and more. While none of these sound too catastrophic, they are often interrelated. As such, they tend to worsen any problem. For example, humor can cause informality, worsen ambiguity, and weaken sincerity. That being said, users should strive to avoid ALL these pitfalls.