General Information

From Claws Mail FAQ
Revision as of 10:29, 29 April 2007 by Claws (talk | contribs) (say something about differences. re: the question)
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What is Claws Mail?

Claws Mail is an e-mail client (& news reader) based on GTK+, running on the X Window System, and aiming for

  • Quick response
  • Graceful, and sophisticated interface
  • Easy configuration, intuitive operation
  • Abundant features
  • Extensibility
  • Robustness and stability

What are the differences between Claws Mail and Sylpheed?

Claws Mail (formerly Sylpheed-Claws) started as the bleeding-edge version of Sylpheed, in order to act as a testbed for new features for Sylpheed. The idea was to regularly resync with Hiroyuki's main branch, and vice-versa. Claws Mail then evolved into the stable extended version of Sylpheed, and is now an entity in its own right, mainly due to different goals and the fact that syncing both codebases doesn't happen anymore.

Claws Mail has many extra features compared to Sylpheed and is more powerful, yet is just as fast, lightweight and stable.

Where can I get Claws Mail?

See the Downloads page

Who writes Claws Mail?

Claws Mail is developed by the Claws Mail Team.

How does Claws Mail store mails?

Mails are stored in the MH mailfile format as used by MH and EMH. Maildir and mbox format are supported via two plugins available on the Plugins page.

Does Claws Mail have mail filtering?

Yes. You can find it in Configuration->Filtering... tab.

Can Claws Mail handle local unix mailboxes?


Can Claws Mail handle IPv6?

Yes, IPv6 is fully supported in Claws Mail.

How many POP3, News or IMAP accounts can I set up in Claws Mail?

The number is unlimited. The limit is reached when your computer stops responding.

Can I set up an Account for sending Mail only?

Yes, set up a new account using Configuration -> Create new Account and set the Protocol to None (SMTP only). Or create a local Account for a MH-directory and disable automatic checking for new mail on that account.

Does Claws Mail support encryption like GPG?

Yes. GPG is implemented and works fine. For activating it in Claws Mail, see the Installation and Configuration section.

How does Claws Mail check for MIME types?

Claws Mail uses the Mutt type of mime checking.

Does Claws Mail allow me to write HTML styled messages?

No. A discussion has gone around over this topic, and the outcome was that HTML mail is not wanted. If you really need to send HTML, you can of course attach a webpage to an e-mail. Several patches have been made to facilitate better HTML handling in Sylpheed. You can find these patches at the Sylpheed Patch Page (see further down in the document).

Does Claws Mail have name completion in the address fields?

Yes. When you search for a name that starts with "don", type "don" (without the quotes) and press the TAB key. This will show you the correct name (when only one "don" exists in your addressbook. Otherwise a dropdown list appears, which allows you to select the name you want. E.g. Donald Duck, Don Johnson. But also e-mail addresses starting with "don" will appear in the list (like "").

Why is Claws Mail so fast?

That's what it is designed for!

How can I send in patches, report bugs, talk about Claws Mail with others?

To talk to others, you should join the Claws Mail users' mailing list at

Can I import an mbox into Claws Mail's MH mailfolders?

Yes, just create/select the folder you want your mails in, and select "Import mbox file" in the File menu.

Can I use procmail to sort my mails with the MH mail handling?

Yes. Just make sure that you add /. to the end of a rule so procmail knows that you are filtering into an MH mail folder. Example :


* ^Subject:.*claws


Check man procmail for details.

When I upgrade Claws Mail, are there things I should be aware of?

Yes, some more critical than others.

You should always read the RELEASE_NOTES document that is included in the release tarballs. The release notes can also be viewed on the Claws Mail Source Forge site Files page listing by clicking the version number of the release.

How can I quickly update the views in Claws Mail?

Just press Alt-U or select "update" from the summary menu.

Why does Claws Mail allow me to open more than one instance at the same time for the same user on a network?

Claws Mail opens a Unix-domain socket using a name constucted from your TMPDIR path plus your UID. This socket is used to arbitrate multiple instances on a given machine. In Linux, at least, named Unix-domain sockets are known only locally, to the creating machine. Pointing your TMPDIR environment variable to /home/yours/tmp doesn't have the desired effect, as the socket definition would need to be propagated across the LAN and isn't.

Does Claws Mail have an anti-spam feature?

Yes. It has a Bogofilter plugin and a SpamAssassin plugin. You can find details of them on the Plugins FAQ Page.

You can also use other spam filters via Actions, futher details can be found on the Using Claws Mail with other programs page.

Does Claws Mail support Return Receipts?


To request a Return Receipt use '/Options/Request Return Receipt' in the Compose window.

When you receive a message that requests a Return Receipt a notification area is shown just above the message view. You can either use the 'Send receipt' button, or ignore the request - no receipts are sent automatically.

Why is Claws Mail slow to load big folders?

Certain options, although handy, slow down Claws Mail:

- Use addressbook to display sender
- Thread using subject in addition to standard headers
- (GPG) Automatically check signatures
- Sort by Subject, From or To instead of Date or other non-string headers
- Processing rules, especially those based on "Whole message" or "Body" contains ...

How do I make a new Icon Theme for Claws Mail?

Obviously you need to have some artistic abilities (well, not much unless you want to make a really cool theme), but, apart from that, there's some technical points you should consider when making a new theme and you want to share it with the rest of the world:

  • Choose a license for it. Remember that themes without license are not free.
  • If you're using some other theme or graphic element you found on the web be careful and check its license also. Some authors use strange licenses which does not allow derivations or redistributions, or impose the original license over derived works.
  • If you're making original artwork and do not know (or care) which license to choose, GPL is a good and recommended option. It's the same license that Claws Mail uses.
  • Try to provide a full set of icons. The easiest way to do that is to copy all Claws Mail icons and start editing them.
  • Keep the sizes uniform. Claws Mail default icons are certain size, and some variations are allowed, but size disparity can not be a good idea if two icons are going to be displayed side to side.
  • Provide a .claws_themeinfo file
  • Have a look at the existing themes, they may inspire you! :)