Send mail from OS X without email account

I have found the solution!

I set up a second email account on my server with an obscure name, then, I changed the POP/IMAP settings to use that account for receiving, and left the send/SMTP details unchanged.

This now gives me the desired behaviour. It also gives me a receive only account ( which could also be desirable ).

If you are on iOS4 or below, you can also refer to Hand-E-Food's answer. My instructions will work for iOS5 ( due to the extra checks iOS5 makes to verify what you've entered )

I don’t think there’s an officially endorsed routine for this, but I’m sure it’s possible; it just depends on what sort of email account it is.

What follows is guesswork based upon poking around the Settings panel of my iPhone. I haven’t tried these methods, but these are what I think might work.

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iCloud

First you need to disable the default iCloud mail settings. On the iPhone, this is Settings > iCloud and toggle the switch next to Mail to Off.

Then we recreate the iCloud settings.

1. Navigate to Settings > Mail, Contacts and Calendars.
2. Select Add Account… in the Accounts list, and select the option at the bottom, Other.
3. Select Add Mail Account from the list of options.
4. Fill in all of your iCloud details, and tap Next.
5. On the next screen, under Outgoing Mail Server, fill in Host Name with smtp.me.com, and the User Name and Password as per your iCloud login. Under Incoming Mail Server, fill in gibberish in the fields.
6. Tap Next. You’ll get some warnings; just tap through them. For example, I have one that says

   This account may not be able to send or receive emails. Are you sure you want to save?

But this is just what we want, so tap Save, and on the next screen, Save again.

In theory, your iCloud account should now be able to send mail, but not receive it. (However, it will probably fuss and grumble, and you’ll still have an inbox for the account, albeit empty.)

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Gmail or third-party mail server

Navigate to Settings > Mail, Contacts and Calendars > Gmail > Account example@gmail.com. Then, in the Gmail Account Information list, delete the Password. (In a third-party mail server, you’re looking for the Incoming Mail Server settings).

Hopefully, if the Outgoing Mail Server still has a correct username and password, you’ll still be able to send mail, but the iPad will fuss and grumble about receiving it.

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I hope this is useful and works; or if not, gives you some ideas as to how to make it work.