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SMTP-Relay Service

The SMTP-relay service supports sending email for devices, such as faxes or copy machines, that can't authenticate properly with an existing email service such as PennO365 or GMail.

Service Overview

Simple Mail Transfer Protocol (SMTP) is the communication protocol used on the internet to send email. The SMTP protocol uses a store and forward technique to accept email from remote senders (servers, work stations or other devices), store it temporarily and then deliver it either to a local email account, or forward it to another server (using the same SMTP protocol) that has been advertised on the internet as the server able to receive email to a specific email address.

ISC maintains an SMTP-Relay service that allows devices to relay email to destinations on the internet. The SMTP-Relay service will accept, store and forward the email to the correct SMTP server on the internet. This allows devices that are not able to implement the full SMTP protocol, such as scanners, lab equipment, etc. to still send email. The service will not permanently store email locally.

The ISC SMTP-Relay service will accept email for email addresses that are part of the Penn email environment. Those are emails that are in the following email domains:

Additionally, the service will accept messages destined for email addresses that are anywhere in the world, if the device sending the email is registered with the service. You can find details on how to register devices with the ISC SMTP-Relay service on the Ordering Service tab. The service will only provide support for clients who have registered their device with the service.

If you need to use the SMTP-Relay service to deliver messages to email addresses not affiliated with Penn, you need to register the name of the device sending the email. To register that device, you will need to fill out the SMTP-Relay service registration form. Once this form has been submitted a staff member will contact the requestor to finalize the registration and set up the service for their use.

Clients that register with the SMTP-Relay service to be able to deliver message to email addresses not affiliated with Penn need to comply with the following requirements:

  • The DNS name of the system needs to be able to be resolved by DNS by IP address. This means that if the name of the server resolves to a specific IP address (the DNS A record), the reverse lookup of that IP address needs to resolve to the registered name (the DNS PTR record). If the lookup of the address does not match the name, or no name can be found, the SMTP-Relay service will not deliver email to non-Penn affiliated addresses.
  • If the system sending messages is protected by a firewall, it is likely that the name that needs to be registered is the name of the firewall and not the sending system. If this is the case, the registering individual takes responsibility for all systems that could use the aforementioned firewall to send email.
  • The SMTP-Relay service should not be used for sending bulk email. The PennNet Mailing Lists service should be used for that purpose. 

Additionally, client software using the SMTP-Relay service is required to use a valid email address as the 'From' address. This is required for the SMTP-Relay service to be able to send a 'Non-Delivery-Report' (NDR) if it cannot deliver the email to an email address. Inability to deliver NDRs by the SMTP-Relay service to the client system will result in suspension of the service for that device. The client software should not use personal email addresses as the 'From' address, but rather use a functional account email address or mailing list.