When you send an email and receive a delivery failure notification, there could be several reasons. We have listed the most common error notifications below:

1. Error: Host name: {server name/IP address}, message: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. Tried 5 time(s)

This notification means that Hai Nhan server has tried 5 times to connect the receiving server, but cannot transfer your email. It may have several problems of hardware or network failures, or even may be the receiving address was wong. Check the recipient's email address for typos and resend.

2. Remote server replied: 552 5.7.0 review our attachment guidelines.

This notification means that there was an error occurred while sending the attachment. For example, several certain types of files have been not allowed by Gmail.

For more information, refer to: https://support.google.com/mail/answer/6590?hl=en

3. Remote server replied: 550 Unknown user.

This notification means that the receiving email address is not available. It may have several problems such as a wrong email address, or its user was deleted/disable.

4. Error Description: Inbox is full. Additional information: The recipients inbox is full.

This notification means that the receiving mailbox is full, cannot receive more email.