when I switch to iCloud, will I lose keychain?

Hello, nope, but Keychain is where your passwords are stored, no real relation to Mail other than it can store your Mail passwoed(s). 🙂

Don't delete you old MM account yet, do this...

I think they're slowly nudging people to switch, .mac & MobileMe are going away about July, may as well set it up now.

I understand .mac & MobileMe mail will still come through.

iCloud Mail setup, do not choose .mac or MobileMe as type, but choose IMAP...

IMAP (Incoming Mail Server) information:

▪Server name: imap.mail.me.com

▪SSL Required: Yes

▪Port: 993

▪Username: example@me.com (use your @me.com address from your iCloud account)

▪Password: Your iCloud password

SMTP (outgoing mail server) information:

▪Server name: smtp.mail.me.com

▪SSL Required: Yes

▪Port: 587

▪SMTP Authentication Required: Yes

▪Username: example@me.com (use your @me.com address from your iCloud account)

▪Password: Your iCloud password