@Sness10 -- for me, that has never happened, either when using Shaw WebMail or Microsoft Outlook.
When using "Reply", the attachment is not included in what is sent.
When using "Forward", the attachment is included in what is sent.
Within Shaw WebMail, if I save the attachment contained in an E-mail message, onto my own disk-drive, then I can delete the attachment, and then close the E-mail message. The message remains, when I reopen it, but the attachment has been removed.