Reprinted from TidBITS by permission; reuse governed by Creative Commons
license BY-NC-ND 3.0. TidBITS has offered years of thoughtful commentary
on Apple and Internet topics. For free email subscriptions and access to the
entire TidBITS archive, visit http://www.tidbits.com/


   Caller ID in Messages Helps to Direct iMessages

   Jeff Carlson

   The Messages app in Mountain Lion confuses the heck out of us because
   we never know where a given iMessage we send or receive will wind up.
   Some people are irritated at having an incoming message pop up on an
   iPhone, iPad, and multiple Macs all at once. There's no hope for that,
   as Apple doesn't yet let you set a single incoming device for iMessage
   based on where your eyeballs are focused at the moment.

   But the contrary problem is also baffling: what if you can't get
   iMessages to appear on all your devices registered with the same Apple
   ID? We figured out the issue, which can let you both turn on that
   'feature' or disable it. The key is 'Caller ID,' a preference that
   appears when you have multiple addresses registered in Messages in
   Mountain Lion or in iOS. (For an iPhone, the phone number counts as an
   address, so even a single email address produces this option.)

   You find the Caller ID setting in Preferences in the OS X Messages app:
   select the iMessage account, and the Caller ID menu appears at the
   bottom if multiple addresses are registered. In iOS, launch Settings
   and then tap Messages > Receive Messages At to find it.

   [1][tn_mountain-lion-caller-id.jpg]

   [2][tn_ios-messages-caller-id.jpg]

   Caller ID defines what the respective iOS and Mac OS X Messages app
   uses as the implicit 'from' address when sending an iMessage to another
   party. When the other person replies, the reply is directed to the
   Caller ID address. That's straightforward enough. But where it gets
   tricky is when you have a different set of email addresses associated
   with each iOS device and Mac.

   For instance, let's say Jeff has jeffc@example.com, jeffc@tidbits.com,
   and jeffc@necoffee.com all associated with Messages in Mountain Lion on
   his MacBook Pro. On his iPhone, he has just jeffc@necoffee.com, and on
   his iPad, just jeffc@tidbits.com. (This isn't just hypothetical; in the
   process of testing, he realized that he'd set up each device with
   different addresses.)

   If Caller ID on Mountain Lion has jeffc@example.com selected, when he
   sends a text using Messages, the reply will return only to his Mac. If
   Jeff changes Caller ID to his jeffc@necoffee.com address, then
   responses come to his Mac and iPhone; if it's changed to
   jeffc@tidbits.com, then to his Mac and iPad.

   Now, Glenn can send Jeff an iMessage to any of those three email
   addresses, and the note will come in to his Mountain Lion chat window.
   But when he replies, Messages in Mountain Lion always changes the from
   address back to his Caller ID address. If Glenn, in turn, replies to
   that and doesn't change the recipient address, his responses go just to
   the devices associated with that email. (In Messages, in the Messages
   window, you can hover over the person's name after the 'To:' label in a
   Conversation, and then click the downward-pointing arrow ' not the name
   ' to switch the account to which you want to address a message.)

   [3][tn_messages_select_address.jpg]

   This provides you with a couple of possibilities.
     * You can ensure that all devices receive all messages, by both
       making sure the same email addresses are entered, or, if not,
       setting the Caller ID on each device to a common email address.
     * You could set up device-specific iMessage accounts and mark them as
       the Caller ID sender, which is a little absurd, but would work. One
       address would be in common across all devices, so for example
       correspondents would use iMessage to reach Glenn everywhere, but
       his replies would come from individual accounts. He could get
       Mountain Lion iMessages at glenn-osx@tidbits.com, while his iPhone
       used glenn-iphone@tidbits.com. When he initiates a conversation
       from a given device, his recipient doesn't need to know that's
       where it comes from; they just reply.
       Of course, this highlights one of the main frustrations with
       iMessage. If someone then stores this device-specific address and
       creates a new message later ' instead of replying to Glenn's last
       message ' they may reply to the wrong place! Also, only iPhones can
       use a phone number as an iMessage account, so it's highly likely
       that a friend will send a text to Glenn's phone number and ignore
       any previous iMessage conversation. So, although you may have a
       small measure of control over which address is sent with your
       outgoing messages, you can't dictate how other people always send
       messages to you without using just one address for all devices.

   This all serves to demonstrate the missing pieces in iMessage. Apple
   seems to not want to provide centralized management of email associated
   with accounts, leaving that up to the individual device. But it does
   validate email addresses that are used with iMessage centrally, and
   confirms that each non-Apple ID address is only associated with one
   Apple ID account at a time. A little bit of help in clarifying what
   goes where, even if it needs a Web site to manage it, or a new
   preference pane, would eliminate a lot of confusion and unnecessary
   fiddling.

References

   1. http://tidbits.com/resources/2012-08/mountain-lion-caller-id.jpg
   2. http://tidbits.com/resources/2012-08/ios-messages-caller-id.jpg
   3. http://tidbits.com/resources/2012-08/messages_select_address.png

.