The ideas listed here have already been implemented by GMX.

implemented
Vote
34
points
In Inbox, checkbox can be added adjacent to every message Posted by sviswanath to Design, 4 Jul 09 at 07:37
In Inbox or any other mail folders, check boxes can be added adjacent to every message. It would make users to easily select messages and perform action like delete or move in one stroke. Currently we are able to perform this functions by ctrl and shift keys. Still this feature would enhance the user experience. [....]
implemented
Vote
642
points
Reduce the Webmail banner/logo height Posted by bradavon to Design, 2 Apr 09 at 03:29
It's much to large and wastes space in Webmail. This is the one that runs across the top of the page. [....]
implemented
Vote
5
points
Messages saved in Dafts marked as Unread Posted by eusty to Mail-Features, 18 Aug 09 at 17:01
When a message is saved to Drafts it's marked as read.

It would be better if it's automatically marked as unread when saved to the drafts. This would then appear on the folder view as Drafts (1) [....]
implemented
Vote
9
points
Mail table: sorted mails showing at the top Posted by Amreck to Miscellaneous, 7 Jul 09 at 15:37
If I go into the mail table, for example the inbox, and click on the icon "attachments", "reply status" or eny other, the mails I would like to see at the top are then sorted to the bottom of the mail table.
This is the opposite I expected and wanted. So I have to click again and wait again, until the mail table is sortetd.

With the first click I would like to see the sorted mails at the top of the mail table. [....]
implemented
Vote
108
points
"Are you sure" message Posted by Waxhaw to Mail-Features, 14 May 09 at 13:56
When closing an email that has not been sent, I would like a pop-up message asking "are you sure". This would save me from losing the message if I accidentally try to close it. It should also have an option to turn this message off. [....]
implemented
Vote
9
points
Spam-Folder Posted by andy to Mail-Features, 30 Mar 09 at 14:22
If the spam protection is disabled, the folder on the left hand side should not be visible. [....]
implemented
Vote
45
points
subject line: stop adding "Re:" on reply Posted by firelovesoul to Mail-Features, 8 Apr 09 at 05:47
Place a script in that looks for "Re:" at the beginning of a subject line => if yes - DO NOT add another "Re:" => if no add "Re:"

Why? Subjects that read "Re: Re: Re: Re: Re: Re: Re: re: Re: An important subject" can get quite annoying. [....]
implemented
Vote
18
points
Opera browser Posted by andyg to Support, 31 Mar 09 at 16:17
I want gmx to work with the opera browser! [....]
implemented
Vote
18
points
US/EN Posted by smash to Settings, 7 Apr 09 at 00:46
I'm not sure if existing at this time, but an option shifting American to British spell check will be appreciated :) [....]
implemented
Vote
183
points
No pop-up window when signing in Posted by JohntheBaker to Mail-Features, 31 Mar 09 at 16:19
Dear GMX,

if you could add a function with which users could either login with the pop up window or directly into the browser, it would certainly be greatly appreciated. Most likely it would ensure a greater convenience for mobile device users!

Thank you very much! [....]