MobileMe: Issues sending messages in Mail or other email applications

1. Open Mail.
2. From the Mail menu, choose Preferences.
3. In the Preferences window, click the Accounts button if it is not already selected.
4. In the Accounts list, if you have multiple accounts, click your me.com or mac.com account.
5. Click the Server Settings button near the bottom of the pane.
6. Verify your SMTP server settings with the following information:
   • Outgoing Mail Server: smtp.me.com (for either me.com or mac.com addresses)
   • Server port: 587 or 25 (some ISPs may block port 25)
   • "Use Secure Sockets Layer (SSL)" should be checked (enabled)
   • Authentication: Password
   • User Name: Your MobileMe member name (without  "@me.com" or "@mac.com")
   • Password: Your MobileMe password

1. Open Entourage.
   
2. From the Tools menu, choose Accounts.
   
3. Click the Mail tab.
   
4. Double-click the affected account.
   
5. Click the Account Settings tab and verify that the outgoing (SMTP) server is: smtp.me.com (for either me.com or mac.com addresses)
6. Click "Click here for advanced sending options."
   
7. Verify the following settings:
   
   • Enable "SMTP service requires secure connection (SSL)"
     
   • Enable "Override default SMTP port:" and enter 587
     
   • Enable "SMTP server requires authentication" and choose "Log on using"
     
   • For Account ID, enter your MobileMe member name (without  "@me.com" or "@mac.com")
     
   • For Password, enter your MobileMe password
     
8. Click the small close box in the upper-left corner of the window, then click OK.
   
9. Close the Accounts window.

If you are using an email application other than Mail or Entourage, consult its documentation to learn how to edit the SMTP server settings, and update the settings to use the information provided above. If you still experience issues after adjusting these settings, you may need to use the SMTP server for your Internet service provider (ISP).

The issue could be due to your Internet Service Provider (ISP) blocking the protocol used to send email (SMTP) from transversing their network. To see if this is the case, please follow these steps:

1. While in Mail, choose Mail Connection Doctor from the Window menu. Wait until there are no spinning gears which will indicate testing is complete. 
2. In the bottom half of your Account Name list, double-click your affected SMTP  account which will have a red dot in the status column. This will open your SMTP settings.
3. Click the Advanced tab and make sure the option to "Use default ports (25, 465, 587)" is selected.
4. If "Use default ports..." is not selected, select it and click OK. 

If your issue persists after this workflow, please contact the support of your ISP (Internet Service Provider) and ask them what their policy is on blocking SMTP traffic that transverses their network. SMTP is the protocol that email uses to send emails. Note: Your ISP may allow SMTP traffic to the email server on their network, so it is important to ask the ISP about SMTP traffic that transverses their network to an external mail service like MobileMe.

If your ISP has a policy of blocking SMTP, ask them how you can be exempt from SMTP blocking.

If your ISP has a policy of not blocking SMTP contact Apple support.