Profile picture guide if you need one on how to set the emails up:
Log in to Gmail: Go to the Gmail website and log in to the account to which you want to add alternative emails.
Access Settings: Once logged in, click on the gear icon in the top-right corner, then select "Settings" from the dropdown menu.
Navigate to Accounts and Import Tab: In the Settings menu, navigate to the "Accounts and Import" tab.
Add Alternative Emails: Under the "Send mail as" section, you'll find an option to "Add another email address". Click on it.
Enter Alternative Email Details: A window will pop up prompting you to enter the alternative email address you want to add. Enter the email address you want to use and click "Next Step".
Verification: Gmail will send a verification code to the alternative email address you provided. Check your alternative email inbox for the verification code and enter it into the Gmail window to verify the alternative email.
Set as Default (Optional): After verification, you'll have the option to set the alternative email address as the default "From" address for outgoing emails. If you want to do this, select the option and click "Next Step".
Profile Picture: To set a profile picture for the alternative email, you need to ensure that the Google Account associated with that email address has a profile picture. You can do this by going to myaccount.google.com, logging in with the alternative email address, and adding/changing the profile picture.
Repeat for Additional Emails: Repeat steps 4-8 for each additional alternative email address you want to add.
Sending Emails: Now, when composing an email in Gmail, you can select the alternative email address from the "From" dropdown menu, and the profile picture associated with that email address will appear if set up correctly.
Please note that the profile picture is an email client-specific feature, we cannot control the picture that is sent because the email protocol does not support it. Gmail can see Gmail account profile pictures because they add extra data on their servers, it is not guaranteed that it will be displayed in other email clients. This is the reason we don't do profile pictures because there is no way to do it. Same in Outlook they also try to fetch it from LinkedIn.
There is a workaround where you can add alternative emails to a Gmail account that has a profile picture and it works, you can add 10 alternative emails to 1 Gmail account.