Receiving email on alias but not able to send any emails - Outlook on the web?

Seeing as this is the leading search result for people with 365 work/business accounts too.

I thought it would be useful to include the solution that will solve this issue here.

To send from Outlook for web or application.

Firstly the end user can't fix this. An admin has to resolve Step 1:

Step 1:

How to turn on sending from aliases in Admin Panel with 365.

By default, sending email from aliases is turned off. An admin needs to turn it on it in the Exchange admin center first.

Sign in to the Exchange admin center. Use your Microsoft 365 email address and password.

Select Settings, then Mail flow.

Select the checkbox next to Turn on sending from aliases.

select checkbox to turn on sending with aliases

Select Save.

Step 2:

Now the user you can send from an Alias!

Thanks Kazi, I wasn't asking to change the default address to use though, I want to be able to send emails from my different alias on occasion by selecting them from the drop-down list of alias options on an outgoing email.

I used to have Microsoft 365 Email Essentials through GoDaddy, which allowed me to set up aliases directly with GoDaddy. For some reason, these aliases worked seamlessly from the start, both in Outlook for Mac and Outlook for iPhone. They appeared in the dropdown list, and I could easily select them on my iPhone while on the go.

However, since GoDaddy restricts domains associated with their Microsoft 365 Email Essentials from being linked with Azure tenants, I switched to Microsoft 365 directly from Microsoft. While this switch allows me to utilize the full capabilities of my domain, I’ve noticed an issue: I could no longer select the aliases I'd added in the Microsoft 365 admin center. These aliases didn’t appear in the dropdown list in Outlook for Mac, Outlook for iPhone, or even Outlook on the web.

So, I began searching the forums.

1. I discovered that, by default, the option to send emails from aliases is turned off in Microsoft 365 from Microsoft. To enable this, I had to go to the Microsoft 365 Exchange Admin Center at https://admin.exchange.microsoft.com/#/settings, select Settings -> Mail flow, and manually turn on sending from aliases.
2. After that, I needed to adjust my settings in Outlook Web. I went to the View tab -> View Settings -> Mail -> Compose and Reply -> scroll down a lot -> find the section Addresses to Send from -> check all the necessary aliases in the list.
3. I also noticed that sending an email from another mailbox to any new alias helps Outlook recognize it, and it will start offering it as an option to select afterwards.

We have this exact issue as well. We want to occasionally send e-mails from alias addresses. How can this be done?

I am trying to send email to and from an outlook alias (not my primary).

When I send an email to the alias, it shows up in my primary box (there is nothing in the alias mailbox) .

If I click on the alias in the Outlook app and click "New Mail," it shows my primary mailbox. The dropdown list does not list the alias. So how do I send/receive mail from the alias?

I tried following the advice above. When I sign onto Outlook on the web with my primary account and select Settings, there is no "Options" choice. Under "Mail", there is no "Accounts" or "Connected Accounts". The support article cited links to an article on Exchange Server 2016.

Is there a way to send/receive mail from the alias?