[Cryptography] How to get certificates on email server?

[Ron Garret]

I presume that by “my email program” you mean an email *client*, not an MTA (like Postfix).  Which client are you using?  Because I’ve never seen a client that give you the option to accept a certificate without allowing you to look at it.  And what port are you connecting to?  The answer depends on whether you are using SMTP+STARTTLS (port 25) or SMTPS (port 465).  (See https://www.fastmail.com/help/technical/ssltlsstarttls.html).

If you’re using SMTPS then you can get the cert using openssl.

http://stackoverflow.com/questions/7885785/using-openssl-to-get-the-certificate-from-a-server

If you’re using SMTP then I don’t know the answer offhand.

rg


On Apr 18, 2016, at 10:52 AM, hbaker1 <hbaker1 at pipeline.com> wrote:

> Stupid question: I'm getting a certificate error when attempting to send email.  My email program says that the certification chain can't be verified.
> 
> Before I accept this dubious certificate, I'd like to look up this server's certificate myself & check it by hand.
> 
> How to do this?  (Either Windows or Linux is fine, since I'm not trying to actually send mail; just check the certificate.)
> 
> Thanks for any help.
> 
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