Gmail is probably the most widely used e-mail provider between creative people. It is always simplistic, modern and always works.

Personally, besides my personal e-mail, I use their "custom domain" feature for handling the e-mails of all my projects.

As expected, the content there is very valuable and hard to risk losing. Gmvault is an open source tool that saves the day by backing up Gmail accounts to your drive smartly.

It can backup the entire Gmail account at once and can synchronize afterwards by only picking the non-backed-up ones (there is also an optional encryption).

If we ever want to restore them, Gmvault can do that as well. They can also be restored to another Gmail address (including labels).

There is a Windows installer and ashell/batch client exists for Linux, Mac OSX and Windows.

E-mail code validation is a painful job considering many e-mail clients/applications have a low-level HTML-CSS rendering support and many others have their own standards. Actually, it is worse than designing for the browser.

Fractal is a free-to-use web application for validating HTML-CSS code across 24 most-popular e-mail clients.

It simply works by pasting the code to the application and finding out if each line is validated, if not, why and in which e-mail clients.

Best of all, Fractal doesn't come with only the bad news but also suggests fixes.

P.S. Besides the desktop and web-based e-mail applications, it also checks the code for the mobile as well.

There are various new and exciting stuff with the website development like HTML5 and CSS3.

But, when it comes to designing HTML e-mails, it is still the tables and hacks for improving compatibility with different e-mail clients.

HTML E-mail Boilerplate is a project which presents a starting point for HTML e-mail design and includes solutions for the major rendering problems with the most common email clients.

The code is very well documented and the download pack includes a non-documented version).

CampaignMonitor, an e-mail marketing service, is sharing 100+ professional, good-looking and free HTML e-mail templates.

They are created by several talented + well-known designers and come with the PSD source files for total customization.

All templates are tested in 20+ e-mail applications including the popular ones like Outlook 2010, Gmail, Lotus Notes, Apple Mail and iPhone.

Allowing users to invite their contacts from other networks or e-mail providers is a popular method used in social networks & web applications.

OpenInviter is an open source PHP class, written in PHP5, for importing contacts from most of the well-known e-mail providers & social networks.

Such an invite feature is great, specially when presented as optional, to gain new users/visitors to any service.

There are already ready to use integrations for:

• WordPress
• Drupal
• Joomla
• phpBB & more.

OpenInviter supports:

• Gmail
• Windows Live
• Yahoo
• Mail.com
• Facebook
• Friendster
• hi5
• Linkedin
• Twitter
• Myspace & more..