Jira incoming mail handler created so many letters

[zaharovvv_suek_ru]

I've created a mail handler for an existing email box. This email box contains more than 1000 letters. And Jira mail handler created more thar 1000 issues.
My thoughts were that Jira mail handler should create only for future new incoming letters.

So, please, answer to my questions:
1. How to turn on mail handler for an existing email box with existing letters(more than 1000 letters) without creating issues for existing letters? Jira should create issue just for new email leters.
2. Why did Jira create issues for existing letters, but not for new letters?

3. What will happen if I move letters into another folder, for example: 'Existed', but inbox("Входящие") will be empty. Will Jira create new 14 issues? Please, see an image:

[Steven F Behnke · Accepted solution]

That's how the implementation works. It reads all messages in IMAP folder and creates issues for each one. Then it deletes the email messages.

1. Jira Reads Email
2. Jira Creates Issue Or Comment From Email 
3. Jira Deletes Email

If you are on Jira Server or Jira Data Center, you may supply your own implementation in the form of a Java Class. 

[zaharovvv_suek_ru]

So is it possible to tune Jira mail handler just for new future email letters, not for existing letters?

[Steven F Behnke]

No. In standard Jira Core and Jira Software you use the standard Jira Email Handlers. There is no way to 'instruct' or 'configure' it to only ingest unread email. The Jira Service Desk (a different application) does perform as you requested as an aside.

The only way that you could accomplish this would be to instead provide a Custom Java Class, if you are on Jira Server or Jira Data Center.

[zaharovvv_suek_ru]

ok, thanks! Could you make an answer to my third question?

[Steven F Behnke]

Pardon, I must have missed that. 

Whether or not to pull from a folder is configured during the Mail Handler (not server configuration) setup.

During the Mail Handler configuration allows you to set a property: Folder Name

If you want to use a TOP level folder named 'Existed', then you would configure the Folder Name to 'INBOX/Existed'. I do not know if email in a nested folder would be read or not. I would suggest moving it to a TOP level folder, alongside INBOX. In that case you could configure Folder Name to simply 'Existed'.