I´m sorry. Maybe I didn´t apply the updates properly. After a complete 
reinstall, things are working as expected.

Then your mail server is broken.

I think this does not entirely solve the issue.

I removed the ~/Maildir folder in order to make a test.

Then, when I click on "Mail" I get the notifications saying the 
folders have beeb created (Sent, Spam and Drafts). See attachment.

And the folder are really created, at least I can see them listing the 
Maildir folder:

duli@sfem-server:~$ ll Maildir/
total 48
drwx------ 8 duli duli 4096 2011-06-06 23:15 ./
drwxr-xr-x 4 duli duli 4096 2011-06-06 23:15 ../
drwx------ 2 duli duli 4096 2011-06-06 23:15 cur/
-rw------- 1 duli duli  248 2011-06-06 23:15 dovecot.index.log
-rw------- 1 duli duli   17 2011-06-06 23:15 dovecot-uidlist
-rw------- 1 duli duli    8 2011-06-06 23:15 dovecot-uidvalidity
-rw------- 1 duli duli    0 2011-06-06 23:15 dovecot-uidvalidity.4ded89ab
drwx------ 5 duli duli 4096 2011-06-06 23:15 .Drafts/
drwx------ 2 duli duli 4096 2011-06-06 23:15 new/
drwx------ 5 duli duli 4096 2011-06-06 23:15 .Sent/
drwx------ 5 duli duli 4096 2011-06-06 23:15 .Spam/
-rw------- 1 duli duli   17 2011-06-06 23:15 subscriptions
drwx------ 2 duli duli 4096 2011-06-06 23:15 tmp/

But when I click on "New Message" only INBOX and Drafts are shown. 
Please, see attachment.

Thanks.

Changes have been made in Git for this ticket:

Bug #10193: Fix regression in saving sent mail in traditional view

  3 files changed, 10 insertions(+), 7 deletions(-)
http://git.horde.org/horde-git/-/commit/a0264eb6c51cc71564de29097b26578d875c9c3a

1. Set IMP config $conf[user][autocreate_special] to 'true'.

2. Create a new user or delete the ~/Maildir of an existing one.

3. Login with *Traditional* view.

4. Set IMP preference "When deleting messages, move them to your Trash
folder instead of marking them as deleted?" to 'true' so you don't get 
the error msg described in Bug http://bugs.horde.org/ticket/10181

5. Click on Mail. A msg is displayed saying special folders (Drafts, 
Sent, Spam and Trash) were created.

6. Click on New Message. The box 'Save a copy in' will be 'INBOX' and 
if you try to change it, only options available in the list will be 
'INBOX' and 'Drafts'.

7. Send the msg leaving INBOX selected. You will get msg "The folder 
"SU5CT1g" was successfully created." (See attached img)

8. Now, delete a msg. It simply vanishes. There is no trash folder 
available in IMP.

If you repeat the same steps, but with *Dynamic* view, then it works 
perfectly. Folders are created just fine and when you send a msg, 
delete one or save a draft, they go to the correct folder (sent, trash 
and drafts).