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Does sending email with TLS help to not being blocked or not being flagged as spam by recipient?

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  • Are you referring to SMTP TLS? (the STARTTLS extension) Sep 27 '16 at 15:19
  • I think it would be difficult to provide a universal answer to this as it depends on the configuration of the spam filter on the recipient's email server. Different filtering engines work differently and they are usually customizable, not to mention that most commercial mail services don't publicize the inner workings of their spam filters. So while use of TLS can certainly be a factor considered by spam filters, it is difficult to know for certain how any particular server will respond to it.
    – tlng05
    Sep 27 '16 at 15:27
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There are two sides of sending email encrypted via TLS:

  • Between the sender and the email provider
  • Between the email provider of the sender and the receiver's email provider (spam filters typically sit here)

The security of the first connection has no impact on the spam rating on the receiver's side.

However, the spam filter on the receiver side might consider the encryption of the inbound connection in his spam rating or even completely deny unencrypted emails.

As tlng05 mentions in his comment, commercial email providers typically don't talk about how their spam filters work in detail. However, as Gmail (just as an example) marks every email that came in through an unencrypted connection with a red lock, it is quite save to assume that encryption has at least a little impact on the spam score - if not technically, then psychologically (at least for Gmail users).

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No. It only protects the email in transit.

Typically, you need to use TLS in two places. Firstly between the two email servers and secondly between the client and their email server.

Trust in the contents of an email is a different matter though clearly if someone has gone to the trouble of ensuring an end-to-end encrypted channel, they are likely to whitelist the sending domain. That would of course most likely make it trusted.

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