Put some thought into your message before you hit “record.” It takes very little time to write a script for yourself to read as you record your greeting. Reading off a script eliminates unnecessary pauses, “ums” and “ahs.”
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.

“Hey, this is [your name] over at [XYZ company]. So anyway I’m about to give in my resignation right now. Please don’t call here again. Just kidding!
"Hello, you've reached [name] at [company]. I'm unable to come to the phone right now. Leave your name and number, and I'll return your call as soon as I'm free. Thank you."