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Have recently switched from Telstra to TPG. How do I retrieve my email from Telstra?
Did you use an email client (eg. Windows Live Mail) with your Telstra email or access it via browser (IE, Chrome, etc)?
If email client, the mail should be on whatever device you used for it.
Otherwise, if your account with Telstra is still active, you could get it via browser, with some effort.
Otherwise, you should talk to Telstra.