To be able to send from an alias address from an iOS device with a primary POP or IMAP account, take the following steps:
1. From the home screen, tap Settings and then tap Mail, Contacts, Calendars.
2. Under Accounts, tap the account name.
3. In the account settings under POP IMAP Account Information, tap Email.
4. Tap Add Another Email...
5. Type the alias email address, then tap the Return key on your keyboard.
6. The alias email address should now be listed below the primary email address. The blue check mark denotes the primary account. If needed, the primary email address can be changed by tapping the email address. Tap the Account name in the upper left corner to go back.
7. Tap Done.
8. To send a message from the alias email address, tap the compose icon in the Mail app, then tap the CC/BCC, From field.
9. Tap the From field again and swipe up or down and select the alias email address. Complete the message and tap Send.