Can i send an email from me.com with an email using a different domain? I have had a dummy email (with a non me.com domain name) address created for my website and this email is redirected to my me.com account. This works fine.

But how can i send email from my dummy address? 
The dummy address is not gmail/hotmail or so on, it is using my website domain name. For far,i have only managed to reply using my me.com account.

Thank you,
Aurélie
On a Mac, in the reply message, notice that the From: line has the down-pointing triangle that indicates that it's a menu. Clicking on it reveals a menu of all the email addresses you have configured. Select the one you want. The response will be sent through the SMTP server you have associated with the account corresponding to that email address.

On the iPhone, the reply message has a consolidated Cc/Bcc/From: field. (You have to swipe down to see it, because it's originally scrolled off the top.) Tap on that to expand it into separate CC, BCC, and From fields. Tap on the From: field, and note that a scrolling list appears at the bottom of the screen, with all your email addresses the iPhone knows about. Select the one you want to use.