How to know they mail see or not

I think you're asking how to know if someone has seen your email or not!

Here are a few ways to determine if someone has opened or read your email:

1. Read Receipt: Some email providers, like Gmail, allow you to request a read receipt. This means that when the recipient opens the email, they'll receive a notification that you've requested a read receipt, and you'll receive a notification that they've opened the email.
2. Open Tracking: Some email providers, like Gmail, use open tracking to track when an email is opened. This means that when the recipient opens the email, the email provider will send a small image request to the recipient's email server, which will be recorded as an "open" event.
3. Click-through Tracking: If you include links in your email, you can use click-through tracking to see if the recipient has clicked on those links. This will give you an idea of whether they've opened the email and engaged with the content.
4. Email Client: Some email clients, like Microsoft Outlook, allow you to see when an email has been opened or read. You can check the email's "properties" or "details" to see if it's been opened or read.
5. Follow-up: If you're not sure if someone has seen your email, you can always send a follow-up email to check in and see if they've received and read your previous email.

Keep in mind that some email providers may not allow you to track opens or reads, and some recipients may use email clients that don't support these features. Additionally, some people may not open or read emails even if they're marked as "read" or "opened".