If you are faced with this problem, sending emails with your mailbox via the browser, check the checkboxes next to "Save copies of sent emails", it is in the settings box. As a rule, letters in this case, it will be automatically saved if they were sent successfully.

With e-mail clients all the more complicated. The letters sent with them are saved in your mailbox on the server, you must configure the client using POP 3 or IMAP with the ability to sync all folders.
For the client Thebat! this process will look as follows:
From the menu select "Create new box", enter your email address and name.
Select IMAP incoming mail server "imap.(the name of the server*).EN", outgoing server is "smtp.(server name).EN", check "My SMTP server requires authentication" (*for example,
Next, enter the email address and password, select "Leave messages on server" and "complete box".
Now select the item in the mailbox properties – "Leave messages on server".
In MS Outlook , the email is also saved by default in the "Sent" folder. It is enough to correctly configure your account: choose in the corresponding box, type the IMAP server and the server information "mail.(server name).EN", then select "email Settings" in the tab "outgoing Server" – "SMTP server requires authentication"– similar to my incoming mail server "mail setup" -> "Save copy in sent".

Also note that Outlook Express is limited to the capacity of the folder, and accordingly, if the file "Sent.dbx" reaches 2 GB, the copy of outgoing messages back becomes impossible, and you want to transfer the data file or deleted.