TLS and SSL encryption in Cloud Office
Transport Layer Security (TLS) and its predecessor, Secure Socket Layer (SSL), are cryptographic protocols that provide security for communications over networks. TLS and SSL encrypt the segments of network connections at the application layer to ensure secure end-to-end transit at the transport layer. For our purposes, they create an encrypted tunnel through which we send plain text emails.
Cloud Office servers by default will attempt a TLS connection for both in and outbound email. For outgoing mail (any of our servers sending to external MX servers), we will perform TLS if it is advertised by the remote server. When performing outgoing TLS, our servers are permissive with the certificate (in other words, if the site is using an untrusted or self-signed certificate, as long as it is a working certificate, we should still accept it).
Our outgoing SMTP servers will use TLS in an opportunistic fashion. This means that our servers will attempt to open an SMTP transaction with the recipient server using TLS. If TLS cannot be successfully connected, the communication will default back to an unencrypted transmission of the data, also referred to as PLAINTEXT.
Also our servers will respond to TLS and SSL requests to send mail to us encrypted.
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