Just like with mailed fundraising appeals, email readers are looking for an excuse to ignore the message. We're all swamped with email even if we receive nothing but spam! A less than compelling subject line provides the perfect excuse to zap your email into cyber-eternity.
The worst entry lines I've seen are simply inexplicable -- using mysterious or nonsubtsantive words like, "signs" or simply the organization's acronym. Others title their emails like distress telegrams: "Donations down," or "Help, need more money." It takes a pretty committed donor to not run from that one.
A better approach? As with all types of fundraising, it's to keep people's eyes on the goal; with intriguing subject lines like, "New program close to launch," or "We did it!" Then you can share the hopeful part of your news or plans -- but explain what funding or other help you need to complete or continue similar efforts. You don't have to believe me -- divide your donors into two groups and give it a try.