Once you have your email aliases configured on your Google, iCloud, Outlook, or IMAP account by checking your email service provider's settings, you can go ahead and add them to your Polymail account.
To add an email alias in Polymail Web and our Mac app:
Click on the small carrot in the lower left corner of the app, and then click on Settings in the menu that appears
Click on the Accounts tab on the left side of the page:
You'll see your email addresses listed here. Click into the email address you'd like to add your alias to.
At the bottom of your account information, you'll see any existing aliases, as well as a blue + Add Alias button. Click that:
To add an email alias on our iOS app:
Open Polymail and click the menu icon in the top left corner (three horizontal lines) to pull up our menu.
Scroll down to the bottom of the menu and click on the gear icon to get to your Preferences.
Find the email account you would like to add an alias to and click it
Scroll down and type in the alias under the Aliases section