When you send a bulk email to your recipients in your Raklet account, you can see who received or not your email. Furthermore, you can see the reason if it is not delivered.
To see the email errors, click on the email that you have sent and then go to the Errors section.
There might be a couple of reasons if the email is bounced or not received by the recipient:
The recipient mailbox is full.
The recipient mailbox is temporarily unavailable.
The server limits are exceeded.
The server is overloaded.
Also, we'd advise you to consider having a Custom Email Sender Name to avoid these kinds of issues.