By default, The Bat! seems to display Japanese fine, but as soon as you try to respond to Japanese messages, or start writing Japanese messages yourself, things go wrong and the Japanese ends up like gibberish: =B!^&@##$)(*)(*#$
I will post how I got this working - who knows, it might benefit someone in the future. There might be other methods and I might even have missed a few things, but at least this works for me.
I will assume that you want to use as much functionality as possible. That means replying to single byte languages in HTML and replying to double byte languages in text format (replying to Japanese in HTML will not work).
1. Make sure all e-mail gets displayed as both HTML and text. This way you can preserve the HTML layout of English e-mails (The Bat! does not support replying to Japanese e-mails in HTML format). Choose Options > Preferences > View HTML messages using HTML and Plain Text version Choose Options > Preferences > View messages with alternative layout (Text and HTML) as HTML and Plain Text version Choose Options > Preferences > Default editor for text: HTML with alternative plain text part 2. If a Japanese e-mail shows up garbled, switch to the text version. 3. If you want to respond to a Japanese e-mail, always respond to the text version. If you want to respond to an English e-mail, respond to whichever version you like. 4. When responding or writing in Japanese, use Shift-JIS or UTF8, but never JIS. JIS won't work.
To speed up the process, I have made separate folders for Japanese clients, which use Shift-JIS as the default charset (I take this pretty far and have separate folders for each and every e-mail contact).
If the above fails, download iconv.dll from http://ritlabs.com/en/products/thebat/download.php and put it in your Windows/System32 directory. Restart your system before using The Bat! again. I doubt whether this has any influence on the current version of The Bat!, but some people say it worked for them. The official instructions from Ritlabs say that this file should be posted in the The Bat! program directory, but on my system the above works while said file is in the Windows/System32 directory. It will probably also work if I delete said file, but I'm not taking any risks... if it works, don't fix it
Thanks to: Wataru Tenga for advice and paving the road at the The Bat! forums James Sparks for feedback and watching me eat my keyboard Alan Siegrist for opening a special mailing list just for me on which I could test things Mika Jarmusz & Kirill Sereda for general encouragements
iconv.dll is not needeed for new versions of The Bat! (like 3.8x)
Currently, The Bat! doesn't properly support Japanese.
We are now working on it, and the Cristmas Release of The Bat! will support Japanese better, although not completely. Most important improvement of Cristmas Release of The Bat! will be full support of Unicode in the attachment file names. You could not use all Japanes characters in attachment files name, but since Cristmas Release this will be possible.
In future we will also eliminate problems with editing and replying.