Outlook
 

Have been receiving a notice from Outlook that they will discontinue my account unless I list my phone number for their records. I'm uncomfortable with doing that. Looking for advice.

Look at the email address and see where it is coming from. This is a phishing attack.

You can block messages from that address and delete the message.

I've never used Outlook. But that's a Microsoft product. They should already have your phone number, assuming you use Outlook. Try logging in to your Microsoft account. If your phone number is there, then there's no problem at all. If you try logging in and get a message instructing you to complete your registration by adding a phone number, then do so.

I have been using Outlook for probably 2 decades, never asked for a phone number. I use the stand alone (non cloud based) product, maybe there are other requirements for the cloud based version.
However, as noted above look very carefully at the address this was sent from Microsoft, if you are not sure here is a link to report spam:
How to report a phishing or spam email to Microsoft - TechRepublic.

Ignore it. Do not click on any links. They don't need your phone number.

You might not remember having ever provided a phone number in order to open a Microsoft account, but you did. It's the only way you can. You have to provide the code you get from a call, to the account login screen, in order to complete the account setup.

But that's basically your "tell" that it's a scam e-mail.

If you have an outlook account, it means they already have your phone number. If you don't have an outlook account, they don't need it.

I've been using Outlook as my primary email address for a couple of decades, never have I received an email stating these terms. Log into your Microsoft account here Microsoft account | Sign In or Create Your Account Today – Microsoft (copy & paste into your browser.) to learn if you provided your phone number when you initially registered your Microsoft account. If not, add your phone number and delete the email received. In any event, do not respond to the email, do not click on any links within the email!

The only valid need for a phone number is for two factor identification. They would send you a text code for you to type.in order to verify it’s you who is signing in.

Microsoft is in the business of selling memberships to their services. If the have a problem with your registration, they would’ve contacted you long ago & not with a threat. Definitely a scam

It’s not true it’s spam! Do you not give them any information or let them into your computer once you do that you’re gonna get a virus. I get the same email

Scam. Been around for years. Im surprised this is the first youve heard of it

Delete it and don't click on any links.

When you say "notice", do you mean email? Of course, you do. Toss it, it's trash. Outlook (the program or website outlook.com which are both Microsoft) does not require your phone number to use those products or services.

I ordered something online from a reputable company and they demanded a phone number before I could proceed with the order so I put in 352-000-0000 and it then allowed me to continue. I don't know if it will work all the time but you can try it. They had my email address to contact me so there was no need for a phone number.

Call them to varify
 

I would not. If you can call them to verify. Way too much crap going on .