There is no way to check if mail has been delivered in Gmail.
How Can I Confirm An Email Was Delivered?

There is no way to confirm that an email was delivered.
The best you can do is to send the email to yourself as well as the intended recipient and check to see if you both receive it.
Why Are My Gmail Emails Not Being Delivered?
There could be a few reasons for this. One possibility is that the email address you are sending to is incorrect. Another possibility is that the recipient’s email server is down or is not functioning properly.
If you believe the email address you are sending to is correct, you may want to contact the recipient to make sure their email server is working properly.
Can You Request A Read Receipt In Gmail Without The Recipient Knowing?

No, the recipient will always be notified that a read receipt has been requested.
Can you recall an email in Gmail after it has been sent?? Yes, you can recall an email in Gmail as long as it has not been opened by the recipient.
Why Are My Gmail Emails Not Being Delivered?
There could be a few reasons for this. One possibility is that the email address you are sending to is incorrect. Another possibility is that the recipient’s email server is down or is not functioning properly.
If you believe the email address you are sending to is correct, you can try resending the email later when the recipient’s email server may be up and running again.
Can You Request A Read Receipt In Gmail Without The Recipient Knowing?

No, the recipient will always be notified that a read receipt has been requested.
Can you recall an email in Gmail after it has been sent?? Yes, you can recall an email in Gmail as long as it has not been opened by the recipient yet.
How Can I Track An Email Without Recipient Knowing?
There is no way to track an email without the recipient knowing.
The only way to track an email is to have the recipient click on a link in the email that takes them to a website where you can then track their IP address.
Why Is My Email Not Being Delivered?
There are many possible reasons why an email might not be delivered. The most common reason is that the email address is incorrect. Other reasons can include full mailbox, mailbox over quota, or the email is blocked by a spam filter.
If you are having trouble sending or receiving email, the first step is to check the email address for typos. If the address is correct, try contacting the recipient by phone or another method to verify that they are able to receive email. If you are still having trouble, you may need to check with your email provider to see if there are any issues on their end.
Why Do Some Emails Never Arrive?
There could be a few reasons.
The email could be caught in a spam filter. The email address could be entered incorrectly. The email could be going to a full inbox. The email server could be down.
Why Is My Sent Email Not Showing?
There could be a few reasons. One reason could be that the email is in your drafts folder. Another reason could be that you accidentally sent the email to yourself.
If you are still having trouble, please contact your email provider for further assistance.