Instituto Superior Técnico

Serviços de Informática

Alert regarding the use of your Tecnico email address with third party email services

It is now common in modern email systems for the email server sending a new message to sign that message with its private key. This signature can be verified by the destination server to validate that the message is legitimate, inasmuch as it was sent by a server authorized to send email for the domain of the “From:” address used in the message. The process is known as DMARC.

This check will fail if the email was originally sent from a server unauthorized for the source address. In this case the message is processed according to a policy that may be the one announced by the domain of the sender address, or one arbitrarily defined in the destination server. As a consequence the message may be rejected (bounced), placed in quarantine, delievered classified as spam, delivered normally, or silently discarded.

The only servers authorized to send email on behalf of Tecnico are the servers maintained at Tecnico. Therefore we must alert our users to never send using third-party email services messages containing as a sender (the “From:” line) your Tecnico email address. If you do so it is likely that some of those messages will be bounced or discarded. We have observed that the policies applied to such messages are becoming increasingly strict  pin all widely used email services and it is likely that these situations will become more frequent.

We are aware that many of our users are using third-party email services such as Gmail to send emails with their Tecnico address. This is one situation likely to result in refused or discarded emails. Our advice is to use an email client (such as Thunderbird or Outlook) configured with two separate accounts (Gmail and Tecnico in this example) in order to avoid possible problems when sending emails. Each account should have its own identity (source address), the corresponding smtp servers, etc, and the program will use the correct set of configurations when answering an email. If you use webmail our recommendation is to use the separate websites for each service.