A few weeks after releasing Thunderbird 3.0, an overhaul of its open-source e-mail software, Mozilla has issued an early test version of a successor that smooths rough edges and fixes some bugs.

A principal change coming with the first alpha version of Thunderbird 3.1, code-named Lanikai, is the inclusion of the Gecko 1.9.2 browser engine, which is the version used in the present Firefox 3.6. The browser engine can be used in Thunderbird for extensions that do things like show Google Calendar or let people take actions in e-mail that require a Web page.

Rafael Ebron announced the new version on a Mozilla mailing list Thursday night. According to the release notes, there are a number of changes:

• Several improvements to IMAP.

• Several fixes for Smart Folders, message filters, and attachment handling.

• Several design improvements and corrections to the interface.

• Download Manager is now accessible as a menu item (Tools > Saved Files).

• Stability and memory improvements.

The full list includes 147 changes in Thunderbird 3.1a1 so far. Obviously, though, expect more as the alpha matures to beta and eventually final release.

Trying to emulate its Firefox brethren, the Mozilla Messaging group that develops Thunderbird is trying to accelerate the release schedule for the software.

reflects a new frequent-release strategy adopted from the better-known Firefox effort at Mozilla.

Dan Mosedale, a programmer for the open-source e-mail software, published the date in a Thunderbird schedule draft he announced Thursday.

“If we’re lucky, we relabel 3.1RC1 [release candidate 1] as final and ship it on Tuesday, April 6. Otherwise, there’s an RC2,” Mosedale said in the planning document.

The new version is due to get an updated Web browser engine. Using the same Gecko project that Firefox is built atop means Thunderbird messages can integrate with Web activity such as Google Calendar.

Another possibility for 3.1 is a revamp of the Thunderbird start page, Mozilla Messaging CEO David Ascher said Friday. That redesign, which Ascher described in May, could show more useful information than the present splash screen–for example, information about what activity people has been up to help pick up where they left off.

“The ‘start page,’ which makes a lot of sense in Firefox, never made a huge amount of sense to me in Thunderbird. In particular, it’s shown only when a folder is selected, and no message is selected. That’s hardly a logical time to show the (colorful, pretty, but fairly useless) page we show now. Instead, why not show information about the selected folder and help people who clearly intended to select a folder, so most likely wanted to do something related to that folder,” Ascher said in the blog post.

The faster Thunderbird release cycle is just one attribute the Thunderbird team is trying to adopt from Mozilla’s higher-profile Firefox effort. Also on the longer-term plan is financial self-sustenance. Those are big challenges, though. An easier adoption will be fun names.

Starting now, Thunderbird versions will be named after beaches, Ascher said in a blog post this week.

“Firefox releases have cool code names while in gestation,” Acher said. “Firefox picks national parks as code names, as metaphors for the values that go into making a Firefox release. The idea made a lot of sense to us, so we decided to follow suit for Thunderbird. Rather than parks, we picked beaches.”

First up: Hawaii. Thunderbird 3.1 gets the name Lanikai, Ascher said, adding that he misspelled it “Lanakai” in the blog post.