What should you do after entering the email subject line?

After entering the email subject line, the next step can vary depending on your intent. Here's a brief overview of each option:

1. **Write your message in the email body.** - This is typically the next step, as you need to provide the content of your email.

2. **Click on "Undo" to edit the email if needed.** - This option is used if you made a mistake and want to revert a previous action, but it's not the immediate next step after entering the subject line.

3. **Click on "Send" to send the email.** - You should only click "Send" after you’ve completed writing your message and made sure everything is correct.

4. **Add email addresses to the "CC" field.** - If there are recipients you want to keep in the loop, this can be done after writing your message or before sending, but it generally follows after the subject line.

In most cases, the correct next step after entering the email subject line would be:

**1. Write your message in the email body.**