The issue with Sender tagged as @mac.com from Mail.app even when @me.com is selected is a known defect. Below is a transcript from my chat session with an Apple Mobileme support rep.
info: Hi, my name is Erica. Welcome to Apple!
Michael Duffy: Hi.
Erica: Hello Michael
Erica: How may I assist you today?
Michael Duffy: I have a question about sending messages from my @me.com adress in Mail.app
Erica: Okay.
Michael Duffy: They go out with a Sender as @mac.com, even though I selected @me.com. It causes other mail servers to see the message as 'sent on behalf of' which causes much confusion for my recipient.
Michael Duffy: I don't have the problem using
http://www.me.com/mail.
Erica: Okay, one moment please while I gather some information for you, so we can troubleshoot this issue.
Erica: Thank you for waiting Michael. I will like you to verify these settings. 1. Open Mail, then choose Preferences from the Mail menu.
2. Click Accounts in the toolbar, then select your MobileMe account from the list of accounts.
3. Click Account Information in the tab bar to the right, then confirm these settings:
Incoming Mail Server: mail.me.com
User Name: your MobileMe member name (do not add @me.com)
Password: your MobileMe password
4. Close the Preferences window and save your changes if asked.
For general Mac OS X Mail setup information, see: Setting up Mac OS X Mail to receive your MobileMe email
Michael Duffy: okay, let me check.
Erica: Okay.
Michael Duffy: The incoming mail server was mail.mac.com. So, I changed that. Everthing else was okay. I'm running a quick test.
Erica: Okay.
Michael Duffy: The messages are still marked with a Sender as @mac.com though.
Michael Duffy: It is properly FROM @me.com, but still has a Sender of @mac.com
Erica: What version of Mac OS X are you using?
Michael Duffy: 10.5.4
Erica: Okay, one moment please.
Erica: I will like you to delete the account in Mail and re-add it.
Erica: Since you're using Mail (the email application included with Mac OS X), you can quickly set up your MobileMe email account. Just choose System Preferences from the Apple menu, click MobileMe, and enter your MobileMe member name and password. The next time you open Mail, it should automatically be set up to check your MobileMe account. For general Mail setup information, see: Setting up Mac OS X Mail to receive your MobileMe email
Michael Duffy: Okay.
Erica: Let me know if you are still getting the same error when your add your account back to Mail.
Michael Duffy: I readded the account -- just testing.
Erica: Okay
Michael Duffy: The Sender is still @mac.com
Erica: Okay, one moment please.
Erica: Thank you for your patience Michael, I'm still looking into this issue for you.
Michael Duffy: Okay.
Erica: Thanks
Erica: Thank you for waiting Michael.
Erica: What I would like you to do is open up your Mail Preferences. And under the account, make sure that you have this listed in the Email Address field:
xxxxxx@mac.com,
xxxxxx@me.com
Erica: You will need both account names separated by a comma.
Michael Duffy: Yes, they are both there.
Erica: Okay, when you send an email, do you have the option to change where the account is being sent from?
Michael Duffy: Yes.
Erica: When you send the email, you are choosing the "@me.com" address.
Michael Duffy: Yes.
Erica: Okay.
Michael Duffy: When I say Sender versus From, I'm looking at the 'long header' option in Mail.
Erica: Okay.
Erica: Have you sent yourself a test email?
Michael Duffy: Yes, I
Michael Duffy: have actually been sending it to my wife's account.
Erica: Okay.
Erica: Are you using Exchange?
Michael Duffy: You mean for my wife's mail? She uses Gmail.
Erica: Okay.
Erica: Thank you for that information.
Erica: I appreciate your patience, as I looked into this matter. Apple is working to identify the issue and expects to resolve it shortly. I apologize for any inconvenience this may cause.
Michael Duffy: Okay. So, you're saying it is a 'known bug' so-to-speak? And I can expect it be resolved?
Erica: Yes. It is a known issue.
Erica: And we are working on getting it resolved.
Michael Duffy: Good enough. Thanks.
Erica: You're welcome Michael.
Erica: Was there anything else I can assist you with today?
Michael Duffy: No, thank you.
Erica: Thank you for chatting with us. We value your feedback. Please click the blue "Close" button at top left to answer a few questions about your experience with us today.
