In many respects this is similar to how support teams might prepare "knowledgebase" articles. There is no panacea to this, you have to decide what constitutes worthwhile knowledge, and filter the emails to locate practical examples of this.
e.g.
From: customer@example.com
To: support@example.com
Subject: Problem with account
Hi,
I'm having trouble accessing my account. Can you help?
Thanks,
Customer
This response is likely to be considered unimportant:
From: support@example.com
To: customer@example.com
Subject: Re: Problem with account
Hello Customer,
I'm sorry to hear that you're having trouble accessing your account. Can you provide more details about the issue you're experiencing?
Regards,
Support Team
But a different response, such as this may be worthwhile:
From: support@example.com
To: customer@example.com
Subject: Re: Problem with account
Hello Customer,
Sorry to hear that you're having trouble accessing your account. Here are some steps you can try to resolve the issue:
1. Make sure you're using the correct username and password. (Check that your caps lock is OFF.)
2. Clear your browser's cache and cookies, and re-try.
3. Try resetting your password.
If you continue to have trouble, please don't hesitate to contact us for further assistance.
Regards,
Support Team
So you must decide which question/answer sets found in email constitute worthwhile learning and then format into an input-output pair for training:
Input: I'm having trouble accessing my account. Can you help?
Output: Sorry to hear that you're having trouble accessing your account. Here are some steps you can try to resolve the issue: 1. Make sure you're using the correct username and password. (Check that your caps lock is OFF.) 2. Clear your browser's cache and cookies, and re-try. 3. Try resetting your password. If you continue to have trouble, please don't hesitate to contact us for further assistance.
Note this will also require stripping emails of all irrelevant information, such as email headers, signatures, urls, marketing etc.
see: https://platform.openai.com/docs/guides/fine-tuning/preparing-your-dataset