There's no single best way to craft an after hours greeting. The most important point is that you equip your customers with what they need to know, and give them an avenue to contact you, whether that's through voicemail, email, or other channels.
Tip: If you’re not sure how to leave a good voicemail, check out the most effective voicemail script ever and how to end a voicemail that keeps the sales conversation open.

Maintenance gives you access to upgrade PBX firmware, check logs and troubleshooting.
A good voicemail greeting is short and professional, lets people know that you’ll get back to them, and invites callers to continue engaging with a call-to-action. You should also show your personality if you’re in an industry or role that allows that. If your industry is more conservative, however, you’ll want to keep humor and personal touches to a minimum. A greeting Your name Your company A simple explanation for missing the call (e.g. you’re away from the phone or are on holiday) A rough estimate of when you’ll get back to the person An alternative person to reach out to (if you’re out of office) An alternative mode of communication (if you prefer email or text) A call-to-action such as “Leave a message” or “Send me an email at [email protected]”