| ID | Error Message | Solutions |
| 1 | Message exceeded the domain's maximum message size limit Message size exceeds maximum allowed size of 26214400. |
Email sent has exceeded the domain size per message limit, please reduce your email content. User might have attached a very large email attachment, do consider send it via third-party file storage |
| 2 | 451 Temporarily unable to process your email. Please try again later. | Receiving/Receipent server rejecting your email, please contact remote email administrator for further assistance |
| 3 | Domain size limit exceeded | You have reached the domain size limit, you need to upgrade or free up the space on your domain to continue receiving email |
| 4 | No such user | Most common reason for this is that sender has mis-typed the email address. Please check the email address of the recipient |
| 5 | The account or domain may not exists, they may be blacklisted, or missing the proper dns entries | Please check the recipient domain name you are trying to send to |
| 6 | Mailbox size limit exceeded | The user's mailbox has exceeded the allocated storage size. User can free up the space by clearing email or increase storage size |
