Adding TLS certificate along with SMTP configuration

Installation
1

I am trying to use my own send-only server to send emails. I am running this SMTP gateway to use TLS because of which the client I use to send emails requires a certificate. I am using a self-signed certificate which is very easily configurable if I use postfix/ssmtp for sending emails but I am not sure how I can use a custom Cert in discourse email client.

Just to get a brief picture in the head:

Easy scenario:
Discourse —send—mail—> mailgun —send–mail—> user

My Scenario:
Discourse —send–mail–> my server running SMTP gateway —relay-mail-using-aws-ses-API—> user

Thank you.

2

I would like to correct my question. So I really don’t need to add any certs for this to work but still its failing to communicate on TLS. If I am testing it with swaks its working fine. Example command:

swaks --to user@example.com --from me@example.com --auth PLAIN --auth-user myusername -tls -s smtp.somehost.com:2525
3

You can directly use the AWS SES SMTP to achieve this why do you want to have a local relay?

4

@itsbhanusharma AWS ses provides 60k emails per month free and as far as I know these email calls should be requested from ec2 instance to work otherwise they are charged as normal. My discourse instance is hosted on a digital ocean droplet. I could be wrong but this is my understanding and the reasoning behind it.

5

So even if Your SES API is receiving emails from a DigitalOcean IP, it would make it chargeable, You may decide to use another service or spin up exim on an ec2 instance to be a bridge between your DO droplet and AWS SES. I don’t think it’ll work but You can try.

It should (in theory anyway) be like:

  1. Discourse (on DO) sends emails to exim IP in EC2
  2. EC2 relays emails received from DO to SES
  3. SES delivers emails to the end user.
1 Like
6

I have already solved the relaying problem by running a local smtp server in ec2 which eventually forwards the smtp request to ses. The problem is discourse is failing on TLS handshake with this smtp server where as postfix/swaks and similar applications are working just fine.

7

Solving that should be as simple as using port 25 (without encryption)

8

Is there a way I can see where this SMTP handshake is handled? Like any library discourse is using in ruby behind the scenes? I don’t want to disable TLS here.

9

Then use a Valid SSL certificate (even letsencrypt should work fine)

2 Likes
10

Using valid cert from letsencrypt didn’t help for some reason. Don’t know why.
But after setting this in app.yaml, emails are working now.

DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none

Someone with more knowledge about SMTP might provide why this is working but I am good for now I guess.

1 Like
11

Does this end up being cheaper than simply moving the discourse instance into S3?

1 Like
12

I have a $ 5 ec2 instance running on aws which I am using for relaying multiple domains. Moving discourse to ec2 would be a little costly from digital ocean, not much to be honest(few dollars over all).

But the point is even if I move discourse to ec2, I would still need that relay service to support rest of the droplets that I have on DO for other domains that I own. So why not just fix discourse :slight_smile:

13

Well, by your own admission Discourse isn’t broken, it interfaces with SES perfectly fine.

You’re doing this to circumvent an SES restriction to relay emails for free.

3 Likes
14

That is true, but discourse has nothing to do with SES here. Discourse is communicating with a SMTP server, which could be anything(right now its a relay service). I was wondering how does postfix/swaks and all are working just fine with this SMTP server(from same DO vpc) and not discourse. After setting that var, it is working though. Still I would like to know what library we are using in discourse for SMTP handshake so that I can personally verify if there is anything we can do to improve in discourse.