My mail program cannot connect to the AWS SES SMTP server

Question

The program that we use for our newsletter emails sends these via email-smtp.eu-west-1.amazonaws.com,  using an SSL connection over port 465.  Logging is done using the SMTP user name and SMTP password that I received for my IAM user name.
This has worked perfectly, for many years.

Unfortunately it no longer works: the program now gives the error
"Error with connecting server;client handshake failed"

When I log in my AWS account does not show any error information.
I tried explicitly opening this port in our router, stopping the virus checker to check outbound emails, creating a new IAM user name in the AWS console and using the new credentials.  No result.
In the Windows Internet Options I also tried what happened when checking "Use TLS 1.3" (instead of Use TLS 1.2): no result
When I enter "telnet email-smtp.eu-west-1.amazonaws.com 465" in a CMD window I get no error  (just an empty screen until I quit telnet).

I have no clue about why this no longer works. Can anyone help me out here ?

Lex

LexLen · Answer

Upgrading my GroupMail software indeed solved the issue.  So this problem had nothing to do with AWS.  Anyway thanks a lot for your assistance in finding a solution.

LexLen · Answer

Hi Shibata,
The program that I use is called GroupMail. It runs on my own PC (Windows 10), that is connected to the Internet via a Fritzbox router. In the Groupmail I can enter all parameters that I mentioned above, the program then connects to the SMTP server and starts distributing our newsletter email. I have been using this program for many years, no changes have bee applied. So I think that something must have changed in the PC, the router or in AWS.

LexLen · Answer

Thanks iBehr,
I just tested, and the result seems OK:

> tnc -ComputerName email-smtp.eu-west-1.amazonaws.com -Port 465

ComputerName     : email-smtp.eu-west-1.amazonaws.com

RemoteAddress    : 52.18.165.220

RemotePort       : 465

InterfaceAlias   : Ethernet

SourceAddress    : nnn.nnn.nnn.nn

TcpTestSucceeded : True

LexLen · Answer

Update: a reply just came in from GroupMail support: it seems that my (old) version does not support TLS 1.2. Strange; I had checked that and since TLS 1.2 was published in 2008 I had not expected this - as the program that I use is much younger.

I will try to upgrade and post about the result.

shibata · Answer

There may be an issue with your mail program. Please explain more about it.

Is the program written in PHP or another language? 
Is it running directly on your computer or in a Docker container or something similar?

iBehr · Answer

I would continue to check your workstation or network.  Connection to the host and port work from my workstation.

```
❯ nc -zv email-smtp.eu-west-1.amazonaws.com 465
Connection to email-smtp.eu-west-1.amazonaws.com port 465 [tcp/urd] succeeded!
```

Hope this helps!

My mail program cannot connect to the AWS SES SMTP server

Relevant content