I am getting the error - "authentication failed" or "sender address rejected" or "Client host rejected" while sending emails over SMTP?

Integrating with Netcore Email API over SMTP protocol is the simplest way of application integration to start sending emails instantly. However, You may come across some common issues/errors while you are at an initial stage of integration. Below given are some of the common errors which may be observed within your application logs along with steps to resolve them,

• Sender address rejected: not logged in: You may observe this error within your application logs if the SMTP username or password configured on your end is incorrect. In order to validate or locate SMTP credentials for your Netcore Email API account you can refer to below link:

https://emaildocs.netcorecloud.com/docs/how-to-retrieve-my-smtp-password-from-pepipost-panel

• Sender address rejected: not owned by user: You may observe this error within your application logs if the sending domain which you are trying to use is not configured or partially configured for your Netcore Email API account. You can validate your current sending domain or add a new sending domain to your Netcore Email API account using the link: https://emaildocs.netcorecloud.com/docs/what-is-a-sending-domain-how-to-set-up-sending-domains
  Note: Please make sure that the sender domain added on your Netcore Email API account is approved and active for use.

• Relay access denied: You may observe this error within your application logs if your application is not passing the SMTP authentication while sending emails. Please verify your application settings and ensure that the SMTP authentication is passed while sending the emails to fix this issue.

Please verify your SMTP credentials and application settings before you start sending emails to ensure that you dont face any of the above errors.