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How do I encrypt emails sent from my server?

Posted September 15, 2017 17.2k views
UbuntuApacheEmailLet's EncryptUbuntu 16.04

The past days I have been working on setting up Email on my server, I have manged to send emails (without them going to the spam folder) but the emails are still not being encrypted.

The server is Ubuntu 16.04 with Apache2 (LAMP stack) - and right now I am sending emails without SMTP (i think) I’m using PHPMailer to send emails.

Here’s the tutorials I have followed:
https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-16-04
https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-dkim-with-postfix-on-debian-wheezy
https://www.digitalocean.com/community/tutorials/how-to-use-an-spf-record-to-prevent-spoofing-improve-e-mail-reliability

For encryption I tried these tutorials, but they didn’t help.
https://www.digitalocean.com/community/tutorials/how-to-use-gpg-to-encrypt-and-sign-messages
https://www.digitalocean.com/community/tutorials/how-to-setup-additional-entropy-for-cloud-servers-using-haveged

Can anyone point me in the right direction? Thanks.

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andersdk
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andersdk
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3 answers
andersdk September 15, 2017

I seemed to find a solution for this at https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-16-04#step-3-—-testing-the-smtp-server in the comment section by the user kevinruffus

He’s comment that solved my problem:

In addition to the instructions above, create your own self-signed certs, use LetsEncrypt, or use purchased certificates/keys (make sure you use wildcard or certificates specific to your hostname/FQDN), and edit main.cf to include:

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/fullchain.pem (change to suit your system)
smtpd_tls_key_file=/etc/ssl/private/privkey.pem (change to suit your system)
smtp_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

smtpdtlsCAfile=(if your cert and CAfile aren’t rolled into a single file)
It cleared the warnings from the emails for me, and shows TLS was used.

Edit: Corrected to show smtpusetls=yes, not smtpdusetls=yes

How to Install and Configure Postfix as a Send-Only SMTP Server on Ubuntu 16.04
by finid
Postfix is a *mail transfer agent* (MTA), an application used to send and receive email. In this tutorial, we will install and configure Postfix so that it can be used to send emails by local applications only — that is, those installed on the same server that Postfix is installed on.
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  • amattu December 12, 2018

    Struggled with this for a week. Thank you so much for this comment.

    Anyone having an issue with TLS, the issue is “smtpd use tls” should be “smtp use tls” take notice to the “smtpd” vs “smtp”

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  • buckley March 28, 2019

    Wanted to add something to this. Your comment is the right way to configure encrypted emails to be sent from postfix on ubuntu but I wanted to add this for people who are wondering about the certificates.

    Most likely you used letsencrypt to make an SSL for your domain, these are stored in /etc/letsencrypt/live/yourdomain.com/

    So the lines above would be changed to
    smtpdtlscertfile=/etc/letsencrypt/mydomain.com/fullchain.pem
    smtpd    tlskeyfile=/etc/letsencrypt/mydomain.com/privkey.pem

    I wanted to mention this because by default there will be a /etc/ssl/certs/ and /private directory but these aren’t setup if you followed the guides above and are using letsencrypt for your web server.

    Google will absolutely mark your email as spam if you don’t have SPF, DKIM, and encryption setup on outgoing emails.

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mariush March 11, 2019

Same thing here, had to change from

smtpd_use_tls=yes

to 

smtp_use_tls=yes

Don’t forget to 

service postfix restart
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danielgc May 18, 2018

Thx @andersdk ! I was having problems with smtpdusetls=yes ! and it was smtpusetls=yes as you correctly highlighted. Best regards.

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