1st QUESTION: When, according to the text, should one never send an email?

2nd QUESTION: What two things should a good email subject line do?

Be very long and detailed in order to explain all the content
Always use capital letters to draw attention
Encourage the recipient to open the message and give them a clear idea of its content
Contain a direct question for the recipient

You should always respond to all emails within 24 hours
The email should not be longer than three paragraphs
The use of emoticons should be avoided in professional communications
If you don't want your message repeated or put on record, don't write it in an email