The advanced set meta data workflow component, Set attachment name sets the name of the attachment for the next email(s) in the current workflow. This can be used with these workflow components e.g. to add an extra attachment to an email:

1. File to attachment
   
2. From file to attachment
   
3. From variable to attachment
   
4. Payload to attachment
   
5. Payload to first attachment
   
6. Resource to attachment
   
7. URL to attachment
   
8. Rename attachment
   

The Set attachment name component has this parameter:

1. Attachment name
   The name of the file, that is attached to the email(s), that are sent from the current workflow. You can press the T-icon on the right to change the input field to an XPath expression and insert a dynamic attachment name.

If you see an attachment name when you receive the email like this:

Then you are probably using an invalid characters in the attachment name. There is no standard as to which characters, that are allowed so you need to test for invalid characters and e.g. replace characters not found in the lists: a-z, A-Z and 0-9. On one mail server the dash (minus) character caused such an attachment name.