Hi, JIQ4
Good day!
Thanks for posting into our community.
According to your description, the issue of your concern that relates to the Teams' speaker and Mic.
Question 1: Yes, a voicemail will still be sent if you record one, even if your speaker is muted. The speaker being muted only affects what you hear, not what the microphone picks up. Since your mic is on by default, it will record your message and send it as a voicemail.
Question 2: Yes, your colleague will be able to hear you if your mic is active and you speak, even if your speaker is muted. The speaker controls what you hear, while the mic controls what others hear from you. So, as long as your mic is on, your voice will be transmitted to your colleague.
I hope this helps! If you have any more questions, feel free to ask.
Merry Christmas and wish you have a great holiday.
Hope you all the best!