Suppose you are writing a quick message and skip the subject like this:
Sometimes it just does not make sense to add a subject to a trivial email. But every email client I tried in the last 20 years will pop up something like this:
An email subject might be helpful but why does it have to be mandatory? Look at how gmail even makes a missing subject no big deal by just displaying a portion of the email body:
Anyway, I understand it might be helpful to enter a subject. So…
What we need is a clear way to inform the user that he or she is about to send an email with or without a subject. And why not just show it as plain text like this:
Now the user is informed and can still send the email with one mouse click. Or the user may add a subject. And if he or she does, we change the text on the button to “Send”:
That way we can ban yet another modal dialog once and for all!