Q: What if I get a "Default Mail Client Not Properly Installed" message?
A: Use one of the other options displayed by the "Reply" button
Q: How do craigslist 2-way relay email addresses work? 
A: Replies to live posts are relayed to poster's email address. Learn more.
Q: I'm getting "message undeliverable" errors. What should I do?
A: Make sure (1) ad is still live, (2) address is correct, (3) no oversized attachments
Q: The reply button won't open.
A: We have received reports of the reply button not displaying a pop-up menu
when clicked. Users have reported success in fixing this issue by taking
either of these steps:

   * Check the add-ons that are installed on your Internet browser. (An
add-on is a browser extension, or a piece of software, that modifies the
browsing experience.) You can view your browser's add-ons by navigating to
the Tools or Preferences menu and clicking on Add-ons. You can disable any
unfamiliar add-ons one by one until the button works.

   * Check to see if you are navigating the web using 'Private Browsing'.
This setting can be found in the Preferences menu of your Internet
browser. Unchecking this and re-starting your web browser may resolve the
issue.

How to reply to craigslist postings

1. Click "Reply."

2. A window with response options will appear.

Reply options box.

To use an alternate email program you will need to copy and paste the reply-to address.

3. Make sure the response address is highlighted and copy it to your clipboard.

Copy blue anonymous email link.

4. Now open your email program and start a new message.

5. Paste the response address into the "To" field.

Paste anonymous email link.

If you successfully pasted the address, it will appear in the "To" field.

Verify that anonymous email pasted.

6. Now compose your response and send it as you would any other email.