- You use two email addresses: email@example.com and firstname.lastname@example.org.
- All incoming email to both addresses is forwarded to your Gmail account: email@example.com.
- You setup Gmail to be able to send messages as either firstname.lastname@example.org or email@example.com.
With this setup, all your email arrives in a unique Gmail account, which can also access through IMAP. When creating a new message in the Gmail web app, you can choose which email should be used as the from address (either firstname.lastname@example.org or email@example.com). When responding to a message, Gmail automatically preselects the address the message you are responding to was sent to, and allows you to override that choice. So far so good.
The only trouble with this setup is when using Gmail's mobile interface, in particular on the iPhone/iOS. The mobile interface behaves as the desktop interface, except it doesn't allow you to change the from address. When sending a new message, it is always sent from your default email (say firstname.lastname@example.org), which means you can't send a new message from email@example.com. Also, you can't override the email chosen by Gmail when responding to messages.
iOS Mail only supports one email per account (unlike the OS X Mail.app) – If you want two email addresses, you'll need two incoming IMAP or POP servers. You can work around this by setting up a Dummy IMAP server as follows:
- Account 1: firstname.lastname@example.org, Unique (real) IMAP, SMTP A.
- Account 2: email@example.com, Dummy IMAP, SMTP B.
When sending an email, you want a copy saved in your Sent folder on your (Unique) IMAP server. You can set this up for firstname.lastname@example.org. But what about email@example.com? Storing outgoing email on Dummy IMAP isn't what you want. You can use the BCC functionality of Mail, and have Mail BCC firstname.lastname@example.org every time you send an email with that address. Unfortunately, at least for those of us using Gmail to handle their email email@example.com, Gmail doesn't seem to be able to forward incoming mail from and to firstname.lastname@example.org, maybe because it doesn't consider it as incoming mail but as sent mail. So you can't forward those BCC to email@example.com, to have them end up in the Sent folder of your unique IMAP server.
When using Mail, with the best possible setup, you can't get the emails sent from one of your emails to end up on your unique IMAP server. Unless controlling what email is used when sending message is paramount to you, and you are fine with, on a regular basis, using a desktop mail client to move the Sent messages from Dummy IMAP to Unique IMAP, you are better off using the Gmail mobile web app.
Hopefully, one day, Google will add the ability for you to select the from email address in their mobile web app, as they already do in their desktop web app: we'll look back, and laugh at how complex it used to be, int the old days, to setup that old iOS Mail.