My Sent from address is gobbledygook

[#1]

When sending e-mails, my address shows up as cÓMc•w°©‘b¤ÄD@plus.com.  If the recipient responds by just clicking on "reply", their response doesn't reach me.
How can I stop this from happening?  (I have a new laptop running Windows Home Premium)

[#2]

The outgoing email address is usually specified in the mail client, depends which you're using as to where that's set but it's usually in the account details. Best bet is to double check it's specified correctly in there, if it is then maybe worth deleting and recreating the account.