External Outlook Webmail not working on Exchange 2013

I configured  an Exchange 2013 on Windows Server 2012 R2, I already obtained a certificate and followed every step here https://technet.microsoft.com/en-us/library/jj218640(v=exchg.150).aspx but I am unable to make OWA work. I can open it internally but not in external network.
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marcusAsked:
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viktor grantExchange ServersCommented:
HI,

Which error do you have when you try to connect in OWA externally?

Error 500?

Cheers
marcusAuthor Commented:
@Viktor I get an error:

"This site can't be reached
ERR_CONNECTION_TIMED_OUT"
viktor grantExchange ServersCommented:
HI,

When you launch the OWA link do you see the correct certificate displayed?
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marcusAuthor Commented:
owa.PNG This is all it shows.
Hemil AquinoNetwork EngineerCommented:
Time out connection means the following:

1- Have you opened the port 443 to accept client connection?
2- Are you pointing your DNS name to your server?
3- Did you allow the the port to be filtered by a firewall?

Let me know how it goes.!

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viktor grantExchange ServersCommented:
HI,

Yes it is correct..it can be DNS issue. Have you pointed correctly DNS to Exchange Server?

It is can be firewall issue too, need to have 443 port open.

Cheers
marcusAuthor Commented:
@Hemil and Viktor

I checked port 443 and it's close. I opened the port and that's it, issue resolved!

Thanks guys!!
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