Send box? Maybe Send Button?

Open a Write window. Do you have a Menu Bar with File-Edit-View etc?

If not press the alt key to make it appear. From the Menu Bar select View-Toolbars and turn the missing toolbars back on. Send is on the Composition Toolbar.

Well worded that wrong; meant the send folder though. On the left side where all he folders are, like Inbox, Drafts. Mysteriously the send folder is gone, so I can not see or recall the send mails.

How can I get it back?

Well worded that wrong; meant the sent folder though. On the left side where all he folders are, like Inbox, Drafts. Mysteriously the sent folder is gone, so I can not see or recall the send mails.

How can I get it back?

Are you using IMAP? Are you subscribed to it? File-Subscribe

IMAP? Sorry don’t know what that is?

Here are 2 email protocols. POP and IMAP When using IMAP you have to subscribe to the folders you want to see with your email client.

When you go to the menu and select File-Subscribe what do you see?

My server setting, using POP