3 ms·
MTA-STS is still vulnerable to MITM. If someone can tamper with DNS queries, it's useless. It's also apparently useless for the first message because the policy
by remram 2y ago
MTA-STS is still vulnerable to MITM. If someone can tamper with DNS queries, it's useless. It's also apparently useless for the first message because the policy will not be in cache and only fetched afterwards.
We could have added a field so that when a server announces that they support STARTTLS, they can say that this fact should be cached for X days.
250-AUTH LOGIN PLAIN
250-STARTTLS
250-STARTTLS-CACHE-90-DAYS
- 8organicbits 2y agoThe vulnerability of the first message is a real concern, MTA-STS is not perfect. But it looks like the easiest to deploy tool that can strengthen security for a very large number of messages. One challenge for your suggestion is that the mail server is often run by a different organization, on a different domain from the receiving address. The HTTPS web server, on the other hand, has a TLS certificate for the mta-sts subdomain of the receiving address. This gives confidence that the MTA-STS policy is set by the receiving domain, not the receiving mail server.