Send over third note, counter tracking packages (6)

I believe the answer is:

remail

I'm a little stuck... Click here to teach me more about this clue!

'over third note counter tracking packages' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'send' is the wordplay.
I cannot quite see how this works, but
'send' could be 'email' (I've seen this in another clue) and 'email' is located in the answer.
A single letter 'r' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Telegraph.

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