Documents will arrive into your recipients' inbox from the email address that you use to log in to Better Proposals.
It's always a good idea to whitelist your sending domain to near-guarantee inbox delivery. You can find out how to whitelist your sending domain here.
If you prefer to send your client a link to the document from your own email account (such as Microsoft Outlook or Gmail):
Click on "Generate links without sending" from the Send page.
You will then see a document link generated per recipient:
You can copy and paste this into your preferred sending method.