You do not say whether you are using a standard Pop account using it's own folders Or a Pop mail account using Global Inbox(Local Folders) OR whether this is an IMAP mail account?

So the answer depends on your setup:

'Tools' > 'Account Settings' > 'Copies & Folders' for the mail account.

• Select: 'Place a copy in'

If Pop mail account using own folders:

• Select : 'Sent' folder on and pop mail account

If Pop mail account using Global Inbox(Local Folders):

• Select : 'Sent' folder on and Local Folders.

If IMAP mail account:

• Select : 'Other' and then choose the Sent folder on imap mail account.
• Note: that sometimes the 'Sent' folder on server may be called something similar eg: 'Sent Items'

Click on OK.

I'm having same issue. I use IMAP and my Server is btinternet.com

Regardless of whether I have folders set up for "sent" mail to go to Sent folder on server or whether I choose "Other" and pick "Sent" folder"; the mail doesn't show up in any of my Sent folders (Sent (sitting right below Drafts), or Sent/Sent Items lower down amongst my other folders.

Yet I *can* see the mail in the Sent folder on my server (the sent folder that sits right below Drafts).

Why am I not seeing my sent mail in TBird?