In Australian English it’s pronounced with the vowel /a:/ like in ‘part’. Problems arise when people use the /ʌ/ vowel (like in ‘up’) instead of /æ/ or /a:/. If you do this is will sound like the worst swear word in English. Many non-native speakers often pronounce the vowel /æ/ more like /ʌ/ because they don’t have a vowel like /æ/ in their first language. Many speakers of European languages will do this (Spanish speakers and Italian speakers) and also speakers of Japanese and Korean. This problem with /æ/ also means that if you say the word ‘back’ in your voicemail greeting sample, you are likely to pronounce it more like ‘buck’. remember to pronounce word endings in English. Check you aren’t dropping any endings off or mispronouncing them.
a personal greeting (as recorded by the mailbox user) followed by the fixed system prompt, "Begin speaking after the tone, then hang-up when you are finished or press any key for further options.

Last but not least a slogan or branding: this is really more important for new customers and people that are calling or leaving a voicemail for the first time rather than returning ones (though it helps a little with them too!). A catchy phrase makes it easier for people to remember your name and recognize you when you give them a call back.
But even that has its limits. "Voicemail transcription still requires customers to leave a message, and they're just not doing that," Boalt says.