410 Labs, maker of a Twitter-like email app called Shortmail that limits email messages to 500 characters or less, announced today that it has raised $750,000 from super-angel Dave McClure’s 500 Startups seed funding firm and others.

The messages sent by — and to — Shortmail accounts are limited to 500 characters or less. That’s designed to keep messages short and simple and also filter out longer spam messages.

The company did not go through 500 Startups’ incubation program, but received a funding from the seed firm. McClure’s startup program is typically known for incubating startups that have some kind of potential to disrupt modern technology. One example is Twilio, a company that develops application programming interfaces (APIs) that let other startups create programs that use text messaging and phone lines.

“I’ve personally been on Dave McClure’s plane trips to Asia,” said Shortmail CEO Dave Troy. “And I’ve been friends with a lot of people in that circle, though we’re doing the East Coast Silicon Valley play.”

The web interface feels like a tablet mail application experience (pictured below). The service also uses IMAP and SMTP email codecs, so it can tie in with just about every mobile email application. That includes the mail application on the iPhone and other desktop clients like Thunderbird and the Mail app for Mac OS X.

“We didn’t go into length limitation on the premise that length is what is wrong with email,” Troy said. “We ran with the notion that email should be for communicating with people and more about relationship maintenance rather than being used as a store for documents and travel reservations.”

Baltimore, Md.-based Shortmail has 7 employees, but the team should grow to somewhere between 10 and 12 people, Troy said. The company also expects to raise another round — likely an extension to the current funding round — by the end of the year, he said.