Can't send email using @me.com address
My iCloud account is a legacy @me.com address. Have been using it without problems for about 10 years. Today I get this message: "Connections to the server p53-smtp.mail.me.com on the default ports timed out". I know how to set SMTP and IMAP access, but there are no screens associated with my iCloud based email that allow editing of any of the normal fields. I have restarted my iMac several times. Force Quit Mail three times, but still cannot mail out. I have tried editing the smtp Server List several times as well, but the accounts will not be deleted. I do have one gmail address, but that's not working either. Any help will be appreciated.
iMac, OS X Yosemite (10.10.3)