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First try basic connectivity to your destination.

telnet smtp.gmail.com 587

If that doesn't work you're probably looking at a firewall issue.

Check that your TLS works

openssl s_client -starttls smtp -crlf -connect smtp.gmail.com:587

If the first worked but TLS fails you are probably using a deep inspection firewall that blocks you from using TLS (because it can't inspect TLS traffic).

Your problem looks more like a firewall issue than an email issue to me.

If it is you need to describe what you have as a firewall & what it's configuration is. If it's purely iptables, which seems possible on your description to date, paste the output of iptables-save.

Edit

Your iptables configuration is blank. The one rule you do have is irrelevant because the default is ACCEPT anyway, so we can safely ignore iptables.

Because you couldn't even establish a TCP connection (telnet smtp.gmail.com 465) this means you are completely blocked by some firewall assuming everything else is working, eg routing and so on. Because this is a production server I think that can be safely excluded.

So you now need to discuss with your network team or look at your external firewall because you are being blocked on port 465.

Just check port 587 as well as per my examples above, just to see if that port is also blocked. In which case you likely have a very restrictive firewall only allowing related, established and port 25.

You will need to add 465 to the permitted outgoing ports on whatever firewall is blocking you.

I don't know your environment but some high security environments do not allow encryption from inside their network and then have the encryption enforced at the firewall. You may be in this or a similar situation.

First try basic connectivity to your destination.

telnet smtp.gmail.com 587

If that doesn't work you're probably looking at a firewall issue.

Check that your TLS works

openssl s_client -starttls smtp -crlf -connect smtp.gmail.com:587

If the first worked but TLS fails you are probably using a deep inspection firewall that blocks you from using TLS (because it can't inspect TLS traffic).

Your problem looks more like a firewall issue than an email issue to me.

If it is you need to describe what you have as a firewall & what it's configuration is. If it's purely iptables, which seems possible on your description to date, paste the output of iptables-save.

First try basic connectivity to your destination.

telnet smtp.gmail.com 587

If that doesn't work you're probably looking at a firewall issue.

Check that your TLS works

openssl s_client -starttls smtp -crlf -connect smtp.gmail.com:587

If the first worked but TLS fails you are probably using a deep inspection firewall that blocks you from using TLS (because it can't inspect TLS traffic).

Your problem looks more like a firewall issue than an email issue to me.

If it is you need to describe what you have as a firewall & what it's configuration is. If it's purely iptables, which seems possible on your description to date, paste the output of iptables-save.

Edit

Your iptables configuration is blank. The one rule you do have is irrelevant because the default is ACCEPT anyway, so we can safely ignore iptables.

Because you couldn't even establish a TCP connection (telnet smtp.gmail.com 465) this means you are completely blocked by some firewall assuming everything else is working, eg routing and so on. Because this is a production server I think that can be safely excluded.

So you now need to discuss with your network team or look at your external firewall because you are being blocked on port 465.

Just check port 587 as well as per my examples above, just to see if that port is also blocked. In which case you likely have a very restrictive firewall only allowing related, established and port 25.

You will need to add 465 to the permitted outgoing ports on whatever firewall is blocking you.

I don't know your environment but some high security environments do not allow encryption from inside their network and then have the encryption enforced at the firewall. You may be in this or a similar situation.

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First try basic connectivity to your destination.

telnet smtp.gmail.com 587

If that doesn't work you're probably looking at a firewall issue.

Check that your TLS works

openssl s_client -starttls smtp -crlf -connect smtp.gmail.com:587

If the first worked but TLS fails you are probably using a deep inspection firewall that blocks you from using TLS (because it can't inspect TLS traffic).

Your problem looks more like a firewall issue than an email issue to me.

If it is you need to describe what you have as a firewall & what it's configuration is. If it's purely iptables, which seems possible on your description to date, paste the output of iptables-save.