Configuration / Settings / Stores / Magento Admin

Scope:

Enabled
File Max Size	File size should be greater than 0 and less than 10 (in MB)
Max File Upload Limit	Automatic: Number of attachment(s) required products in cart will be the maximum limit
Max File Upload	Maximum file can be upload (Range 1-30).
Extensions Supported	File extension will be comma(,) separated like (pdf,jpg,jpeg,png,doc,docx).
Expiry Enabled
Expired After (In Days)	Minimum 1 and Maximum 30 can be set.
Attachment Notifications To Admin

Customer Email Template
Admin Email Template
Admin Uploads Attachment Email Template

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