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How do I set up the Sendio ESP to work with one or more hosted mail servers?

By March 25, 2018August 11th, 2020FAQs

Your Sendio ESP can be configured to handle multiple domains for multiple customers. The Sendio ESP can forward e-mail for each customer to their mail server, whether they have one on premise (Exchange or other) or whether their e-mail is hosted by a mail hosting service. As an example, let’s assume we are setting up the Sendio ESP to handle e-mail for a sample domain, call it and also assume the mail server is hosted. The following needs to be done:

  • Add “” as an entry under the Domains section.
  • Double click on it and set the Organization Name option appropriately (e.g. “Acme, Inc.”).
  • Set the “Internal Mail Host” to the IP address of the hosted mail server.
  • If the hosted mail server for this domain has an LDAP Compliant directory server which can be accessed from the Sendio ESP (typically by opening up port TCP 389 or TCP 3268 to the mail server) proceed to create an entry under the Directories section so that the list of mailboxes/e-mail addresses are “pulled” from the hosted directory (we can help with the specific settings if needed).
  • If the directory is not available at the hosted environment, you can use the onboard LDAP server instead. To administer this server, you will need to download a program called OpenLDAP Browser at the bottom of and use that to create an OU (Organizational Unit) for the domain and then create entry for each mailbox/user. Once this is done, a new entry needs to be added under the Directories section that will synchronize with the onboard LDAP directory (contact Sendio Support for help).
  • Test the setup by simulating an inbound e-mail from an external address (e.g. [email protected]) to a valid address at Use the E-mail Test section located in the console interface under the Network Diagnostics.
  • Route e-mail for domain to the Sendio ESP by changing the domain MX record.
  • Once the MX change propagates throughout the Internet, the last step is to lock down the hosted mail server so that it accepts anonymous SMTP connections ONLY from the Sendio ESP and nowhere else.
  • Failing to do this will allow spammers to deliver spam to the hosted mail server and effectively bypass the Sendio ESP