SmtpClient fail to send email using Amazon SES endpoint
I'm using .Net SmtpClient to send emails with Amazon SES.
The emails can't be sent from some PCs and I get a timeout.
I read the Amazon doc -> https://repost.aws/knowledge-center/smtp-connectivity-timeout-issues-ses
I'm investigating if this could be a TLS issue, because the command they ask to run doesn't complete (which is probably causing the SmtpClient timeout issue as well)
openssl s_client -crlf -starttls smtp -connect email-smtp.us-east-1.amazonaws.com:587
[EDIT]
I've run a Wireshark trace on a Working PC
And then on a non-working PC
I'm not sure what it means... Any thoughts?
Thanks!
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Hello.
What about doing a packet capture using something like "tcpdump"?
Regarding the "tcpdump" command, this answer may be helpful.
https://repost.aws/questions/QUlQYKoGVNQkuKY_bdyU5DNg/ses-update-tls-connections-to-1-2-to-maintain-aws-connectivity#ANuiqMgNVxTLqHA90aDR7SWw
I don't think it's very likely, but could it be blocked by the OS's firewall?
Using Wireshark, I see there is a difference in the network trace between a working/non-working environment. See my Edits with screen capture in my original post.
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Side note, the emails works on most devices in my inventory but does not work on 2 specific computers.