Can Let's Encrypt certificates be used for email signing?

Hello, engineers.

Can you, please, suggest, can LE certificates be used for email signing?

In my case,

le cert isn't s/mime certificate, although it can be used for sign smtp server


No; Let’s Encrypt offers Domain Validation (DV) certificates.
And see Does Let’s Encrypt issue certificates for anything other than SSL/TLS for websites?

1 Like

Yeah, although following that link to "" it looks like an SMTP server of some sort, and domain-validation certs from Let's Encrypt work fine for authenticating and encrypting server-to-server SMTP connections. I have no idea what exactly this user is looking for here, though, or how one integrates certificates into that software package.


Thank you all for your replies.

I have tried to configure poste mailserver using LE certificates, but but it have not seen LE certificates and using it's own self encrypted one.

When I buy a GS, all works. Works - mean web UI and all clients - android gmail, thunderbird works ok without any cert configuration complains.

So, my questions are - did I failed in configuration or it's impossible to use LE for own email server? If I was wrong, I can elaborate in soon time.

1 Like

It's entirely possible to use Let's Encrypt certs with a mail server; I've been doing it for years. It is not possible to use them to sign emails; that would require a S/MIME cert, which Let's Encrypt does not issue.


I don't think so.

It is possible for an LE cert ot be used by an email server.

That said, it might be the case that some clients will not work with some LE cert chains.
It depends on which chain was used (long or short) and the client version being used.


This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.