Hi @Chatwarun ,
According to your statement, a schedule flow which starts on 15 every month will work for you.
Suppose your 15 files are saved in the same folder in Onedrive, here're detailed steps for your reference:

Set start time to 7/15 and interval to 1 Month, the flow will be triggered at 15 each month.

Then initialize a variable to store attachments later. List files in target folder.

Append each attachment to the array variable.

Finally we can send email with the attachments variable:



Hope this help~
Community Support Team _ Wenjuan Zou
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