Like others, i cannot get send from alias to work. Sent emails always come from the main email user!

The alias must be added to your Microsoft 365/Exchange Online mailbox; configuring it only in GoDaddy cPanel can deliver incoming mail but does not register it as an address from which Exchange Online can send.

Add the alias to the Microsoft 365 mailbox

1. Open the Microsoft 365 admin center.
2. Go to Users → Active users.
3. Select your user.
4. Under Aliases, select Manage username and email.
5. Enter the alias, select your custom domain, and choose Add.
6. Select Save changes.

The alias must use a domain available in the domain list. Microsoft notes that changes can take up to 24 hours to propagate.^1^

Alternatively, in the Exchange admin center:

1. Go to Recipients → Mailboxes.
2. Select your mailbox.
3. Open General → Email addresses → Manage email address types.
4. Select Add email address type → SMTP.
5. Enter the alias, select the domain, and save.

Afterward, the address should appear among that mailbox’s Exchange email addresses. An Exchange proxy address delivers into the same mailbox and identifies the address as belonging to that mailbox.^2^

If you manage Exchange Online PowerShell, the equivalent operation is:

Get-Mailbox [Email] |
    Select-Object -ExpandProperty EmailAddresses

Set-Mailbox [Email] `
    -EmailAddresses @{add="[Email]"}

Get-Mailbox [Email] |
    Select-Object -ExpandProperty EmailAddresses

The final output should include smtp:[Email].

Test from Outlook on the web

After Exchange shows the alias:

1. Open Outlook on the web.
2. Go to Settings → Mail → Compose and reply.
3. Under Addresses to send from, select the newly added alias.
4. Start a completely new message.
5. Enable the From field if necessary, then choose the alias from the list.
6. Send to an unrelated external address and inspect the received message’s actual From address.

With SendFromAliasEnabled enabled, Outlook on the web exposes mailbox aliases as selectable From addresses.^1^

Do not type an arbitrary cPanel address into Other email address unless it now appears on the Exchange mailbox. Selecting or typing an address in Outlook does not itself grant Exchange permission to send as that address.

GoDaddy-specific condition

If the Microsoft 365 subscription was purchased through GoDaddy or another partner, some address-management operations—particularly changing the primary address—must be performed in the partner’s management console rather than Microsoft 365 admin center.^1^

If mysite.com is absent from the domain dropdown, the missing prerequisite is that the domain has not been added and verified in that Microsoft 365 tenant. Adding the address only in cPanel does not satisfy this requirement.

Outlook client behavior

First establish that sending works in Outlook on the web. Microsoft specifically documents alias selection there. It also documents that Outlook desktop can use the primary address when replying, depending on the Outlook client.^1^

If web mail still rewrites the sender after the alias appears on the mailbox and propagation has completed, collect:

• The mailbox’s EmailAddresses output.
• The result of Get-OrganizationConfig | Format-List *SendFrom*.
• The received message’s Internet headers.
• Whether the subscription is administered by GoDaddy or directly by Microsoft.

Those details distinguish an Exchange configuration problem from behavior introduced by the GoDaddy/cPanel mail routing arrangement.

References

1. Add another email alias for a Microsoft 365 business subscription user
2. Add or remove email addresses for a mailbox in Exchange Online