Claws Mail: The unsung powerhouse email client

Jack Wallen
Jul 4, 2009
Updated • Jan 14, 2013

I have used so many email clients over the years. For the last few years my go-to email client has been Thunderbird. Lately, however, I have really been taken in by Claws Mail. Claws Mail is an email client for power users looking for more than just your average email client. Claws Mail has more features than the average email client and is just as reliable as anything you have used.

Claws Mail is based on GTK+ so it will install on nearly any Linux machine running X Windows. It features:

  • Multiple Accounts
  • Threaded Display
  • Filtering
  • IPv6 support
  • Mbox import/export
  • Clickable URLS
  • Addressbook
  • Granular configuration
  • Pre and Post processing filters
  • Redirecting
  • SSL Certificate Manager
  • Address Harvesting via folder or messages

And much more.

Getting and installing

If you open up your Add/Remove Software utility and do a search for "claws" (no quotes) you will find numerous listings. Many of these listings will include a vast array of plugins available. The minimum you want to install is:

  • claws-mail
  • claws-mail-extra-plugins
  • claws-mail-plugins

jWhat the "extra-plugins" will do is install a number of the basic plugins for you. Outside of that you will want to go through the list of all the possible candidate to see what you will need. I also installed:

  • claws-themes
  • claws-mail-pgpinline

Your needs may dictate other installations. There are thirty-three possible packages to install.

Once you have made your choices click Apply to finish up the installation. Once installed you will find the Claws Mail menu entry in the Internet menu of your Main menu.

First Run

When you first open up Claws Mail you will have to walk through a very straight-forward wizard to set up your account. Once you are finished with the account set up you are ready to rock.

The user interface

Figure 1
Figure 1

As you can see (in Figure 1) the interface will be familiar to anyone that has used any email client of any nature.

One of the first things that might be of issue (at least it was for me) is the date. Notice that the form of the date is YY/MM/DD. If you want to edit the date format you have to open up the Preferences window by click the Configuration menu in the main window. Once inside that window click the Summary sub-section of the Display section. Scroll all the way down until you see the Date Format text area. The default is set up as:

%y/%m/%d(%a) %H:%M

You can arrange this any way you like. My preference is:

%m/%d(%a)/%y %H:%M

NOTE: The (%a) displays the day of the week.

Importing mail box

I had 100% success at importing my Thunderbird Inbox with Claws. To do this click on the File menu and select "Import mbox file".  A small window will open up where you need to locate your Mbox file and a Destination folder. For a Thunderbird Inbox file you will need to then navigate to:

~/.mozilla-thunderbird/XXX.default/Mail/Local Folders/

and select Inbox (or whatever folder you need to import).

Where XXX is a random string of characters created upon installation of Thunderbird.

In Figure 1 you will see some 8,000 imported emails. It worked perfectly.

Harvesting addresses

Figure 2
Figure 2

This is one of my favorite features of Claws Mail. When I have had to move from installation to installation, one of the things I tend to forget it to export my address book. This isn't a problem with Claws Mail. With all of the email imported into Claws Mail I can then just harvest all of the addresses I need from within a folder. To do this I allow email to collect in my Inbox and then click on the Tools menu and select the Harvest submenu and then the "From Folder" entry. A small window will open (see Figure 2) where you give your address book a name, a size, and tell the harvester which header field to harvest from. Once you do that click OK and the harvesting will begin.

From within my 8,000+ emails the Harvester grabed over 1,400 addresses. The only problem is the Harvester isn't terribly intelligent as to how to label these addresses. So most likely you will have to go back through and edit each address.

Final thoughts

You can go through all of the features, one by one, of Claws Mail and spend all day tweaking and tinkering. As I said, Claws Mail will make the power user feel right at home. But don't think this client is only for the elite user...Claws Mail can be used by anyone. It's easy, it's powerful, it's reliable, and it's all about Linux. Give Claws Mail a most likely won't turn back.


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  1. Angelo Neuschitzer said on April 14, 2014 at 1:55 pm

    Hi, I used one of your screenshots here: Hope you don’t mind. If you do, drop me a line and I’ll remove it.

    Angelo Neuschitzer

    1. Martin Brinkmann said on April 14, 2014 at 2:10 pm

      Angelo that is fine, no problem at all. Thanks for letting me know.

  2. Partho Banerjee said on December 29, 2011 at 11:56 am

    Forgot to add, Sending HTML emails may be only frontier that many people may like Claws mail to cross. Make no mistake, you can easily read HTML emails using plugins but but sent without using an attachment. It’s not a critical feature for me so I am not complaining.

  3. Partho Banerjee said on December 29, 2011 at 11:53 am

    I have used Outlook, Evolution, Thunderbird and now Claws.

    Outlook is proprietary and MS, so ruled out along with Windoze :-)

    Evolution — it can’t recognize ppp (dial up network connections) like USB modems and hence will not allow me to go online. That’s plain stupid no matter other good qualities. It stops me right at the beginning if I am not using LAN or WLAN (Wifi). I use 3.2 mbps broadband USB modem (Huawei).

    Thunderbird– very good and “perfect” looking but chews up lot of memory, going more rigid with every release and recently pained me heavily to connect my yahoo and gmail during new account creation, which Claws got me in the first attempt using same settings.

    Claws is very lightweight but not light of features. It has enough to keep both beginners and power users happy. I think one will become a “power user” with Claws in a short time. It has a bare minimum list of plugins and “themes” and is thin on bells and whistles. Thank God.

    When you want to play like a kid, Thunderbird has all the bells and whistles for you. But when you want to get serious and settled down in (emailing) life, think of Claws.

  4. Dotan Cohen said on July 11, 2009 at 3:10 pm

    I see, Jack, thank you for the explanation.

  5. Colin said on July 5, 2009 at 10:00 am

    AC: MH is a standard, that we find better (more robust and faster) than mbox.
    mule: you seem to be confused, IPv6 support doesn’t mean TCP/IP stack.
    Rather, it means that Claws Mail uses the IPv6 compatible APIs so that it can
    connect to IPv6 servers. Surprising as it is, it’s not yet the case of every networked app.

  6. paulus said on July 4, 2009 at 9:06 pm

    Thanks Jack that tools does the trick for me.

  7. Jack Wallen said on July 4, 2009 at 8:56 pm

    paulus: which client would you be thinking of migrating from? when you install there is a packaged called “claws-mail-tools” that provides scripts for migrating addressbook conversion, etc. it would be smart to install that along with the rest of the packages.

  8. Jack Wallen said on July 4, 2009 at 8:38 pm

    Dotan: Yeah it’s crazy isn’t it…that’s the way we are taught here in the states – unless you are in the military. In the US military it’s:
    Which does make sense. But outside of the military we say (for instance today’s date):

    July 4th, 2009.

    So MM/DD/YY is correct.

  9. mule said on July 4, 2009 at 4:47 pm

    Since when is a TCP/IP stack a feature of a mail client?

  10. Dotan Cohen said on July 4, 2009 at 2:17 pm

    “My preference is: %m/%d(%a)/%y %H:%M”

    You put the day between the month and the year? You do realise that years are bigger than months are bigger than days, right? So it should either be %y then %m then %d if you like the least significant unit last, or %d then %m then %y if you like the most significant unit last.

    I don’t suppose that your wristwatch is configured for HH:SS:MM by any chance?

  11. AC said on July 4, 2009 at 1:50 pm

    Nice review — but I was disappointed to read elsewhere that Claws does not use the standard .mbox format for local storage. Is there any advantage of their own MH format over mbox?

  12. TJ said on July 4, 2009 at 10:29 am

    Same as Paulus, My question is, if this client can sort emails like Gmail does.

    I have hard time figuring out which mail client I should settle on. At the moment, I have Outlook, Thunderbird, Postbox. I tried Zimbra but it crashed while update, removing all installation without my notice (leaving email files as it is) so I lost trust in Zimbra.
    Thunderbird seems to have lost its thunder now, no new plugins coming up, old ones are not getting updated, leading to incompatibilities and it doesn’t sort like Gmail, so not preferred one.
    Outlook, proprietary and no support for Gmail like sorting but easy to port due to large user support, not preferred one either.
    Postbox, sorts mail like Gmail (works still needed) so if they polish it very well, I will keep using it, even if now they are planning to charge for it.

    My ideal mail client, will have only one mailbox where all emails are collected, will give me an option to tag each email for the mailbox it came in from, sorts email like Gmail (MOST IMP), restricts certain mail addresses to certain email accounts (so that I don’t write them mail from another mail ID, restricting work and home communication to the respective IDs) etc. etc.

  13. paulus said on July 4, 2009 at 9:47 am

    Before i give it a try i have a question for you Jack, i found in the faq: How can I convert my old mailbox / addressbook from (some mailclient). In the source distribution, you can find some scripts in the tools subdirectory, maybe your application is supported. This do not answer main question or i can set over/converd main outlook adres list? Do you know this?

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