To make sure Apple Mail (Mac Mail) settings are properly configured please check your install with the following tutorial.
1) In Apple Mail (Mac Mail), go to "Mail" > "Preferences..."
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2) Select the Accounts tab. Under Account Information, click the drop-down next to Outgoing Mail Server and select "Edit SMTP Server List..." (See image below)
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3) In the same screen shot above go ahead and select Advanced tab. (red arrow pointing with 3 next to it)
4) Under the Authenticaion drop-down, ensure Password is selected rather than MD5 Challenge-Response.
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5) Click OK button to close the SMTP window. Then OK button again to close Preferences. And you're done!
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END OF TUTORIAL