It's offline - it build an email archive which is updated whenever you tell it to sync with your mail store(s).
I really like it a lot and they are responsive to new ideas and reply to support requests.
My only wish list would include allowing the free version to have more than 3 profiles (the current limit) ... but having said that since I use Outlook and they now support IMAP as part of your Outlook Profile that is effectively solved for me.
For me the big advantage is the speed of searching your archive - plus you have a separate copy of all important emails incase of file corruption in you normal client.
thanks for the hint I Will have a look at it
too bad, that The Bat! is not supported.
By the way masu I think there is a simple solution to lack of The Bat support (at least for incloming mail from now) ... just set up a POP profile and download mail to MailStore direct from the server. If you set up The Bat to not delete emails from the POP server for 30 days you would only need to sync once a month. This should work for any POP based account whatever client you are using.
It doesn't solve the problem of your existing email store - can you export everything to Outlook Express and then import from there as a one off exercise? Sorry it is a long time since I tried the Bat but I seem to remember the thing I liked least was the proprietary format and lack of import/export options.
Just looked at MailStore FAQs and this might help:
TheBat! wird nicht direkt von MailStore unterstützt. Sie können jedoch grundsätzlich immer versuchen, die E-Mails im .eml- oder MBOX-Format zu exportieren und mit MailStore über den Importweg "Dateisystem" zu archivieren.
Which roughly translates as "The Bat! isn't supported directly but you can export emails to .EML or MBOX format and then import them into MailStore."