iPhone users seem to have a problem with the latest version 2.0 update in which MobileMe email accounts all send mail through the primary email name. This means that for accounts which are set up with email alias names, the iPhone software will not send email with a "reply to" address as the alias, but instead use the main account name as the reply email address. As described by one Apple Discussion member:
As described by Apple Discussions poster 24Golfer:
"If you use Alias email names and receive emails as you normally would - and reply to an email from your Alias - it still sends it out from the proper account instead."
There currently are no direct fixes for this problem for iPhone users, as full support for email aliases will require an update from Apple. However there is a method for bypassing Apple's MobileMe SMTP servers to get mail sent from alias account names. The fix for Apple's Mail application is a more straightforward setup issue.
However, you can workaround the issue as follows:
Use Gmail as a pipe for handling aliased MobileMe names While the iPhone cannot fully handle MobileMe alias names, it can connect to Google Gmail accounts which can be used as a middleman for sending email via the alias names. The process to do this is as follows:
Set up a Gmail account Go to http://www.gmail.com and set up a free Gmail account. Then under the gmail settings go to the "Accounts" section and under "Send mail as:", click the link to add another email address and enter the MobileMe email alias account (a confirmation email will need to be sent to the account).
Configure the iPhone to use the Gmail account SMTP server In the iPhone's settings, go to the mail section, then to MobileMe, and get to the "Account Info" section. Select "SMTP" and add the following server "smtp.gmail.com". Then use the new gmail name and password as the authentication information, and save the settings. Ensure the SMTP server for Me.com (smtp.me.com) is disabled.
NOTE: While this process has been outlined for Gmail, other free webmail accounts may also work if they support both sending mail as another account name and setup via alternative mail clients.