If you’re noticing that the emails you’re sending from inFlow On-Premise doesn’t sync into your “sent” folder, your email account is probably set as a POP3 account. When your email account is configured as a POP3 account, only the items in your Inbox folder of your webmail account will be synced with the server (that your emails are stored in).
To change this behaviour so you can see the sent emails from inFlow in your sent folder, you’ll have to switch to an IMAP account. An IMAP account does a complete sync between your email client and the server, so your emails sent from inFlow will be synced. There are different instructions for how to switch from POP3 to IMAP, but please consult with your email service provider or try taking a look here.
If you cannot or do not wish to switch from POP3 to IMAP, another workaround is to BCC yourself when you send an email from inFlow so you can see it in your inbox.