Keep unresolvable text symbols when maintaining emails

Some text symbols (placeholders) cannot be replaced when creating a new document, e.g. the document number is unknown before saving the first time.

If the e-mail is maintained in dialog these placeholders are removed as the placeholder is initial.

e.g.

Subject: "Purchaseorder &EKKO-EBELN& / &EKKO-EKGRP&

is replaced by

Subject: "Purchaseorder / 123"

If changing the subject in dialog the text symbol is permanently removed. Same applies to mailtext.

Possible solution:

If a text symbol cannot get resolved as it is currently empty, the placeholder should be shown in dialog. So with above example when calling the dialog the subject should be "Purchaseorder &EKKO-EBELN& / 123".

When the subject is changed by the user and he keeps the text sybol it should be still replaced during sending.