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I have an Exchange 2013 Server.

My ISP blocks port 25 and it doesn't seem to be working on any other port either.

I am currently using DynDNS' hosted SMTP service - but it only lets me send a few hundred with each subscription.

What is the best way of setting up something that would allow me to have an SMTP that works? Is there a way of setting up an Exchange server as some sort of relay server and then proxy the main send connector into it? Maybe in Azure?

William
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    Get a new ISP. Seriously. Or at least talk with them and ask them to remove the block. No legit commercial ISP should be blocking 25. As a last ditch solution, you could establish an IPSec VPN to an external host and route your SMTP through there, but that's quite ugly. – EEAA Dec 30 '13 at 03:21
  • It's Verizon Small Business - I have a hunch that there is something screwed up on their end because it is a little absurd that they block 25 (event though it's a small business line instead of an enterprise one). From your reaction, it seems like I need to look into other ISPs - even if it's just for my mail server - – William Dec 30 '13 at 03:27
  • Yeah I've had ISPs that happily opened outbound port 25 for me once I just asked them to. – Ryan Ries Dec 30 '13 at 03:28
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    It *does* make sense if ISPs block port 25 by default; but accounts with static IP addresses almost always can have the block removed, you just have to ask. Else, indeed, you'd probably be better off switching! – cnst Dec 30 '13 at 05:19
  • Why not just forward all your outbound email to your ISP's mail server and let it deliver for you? – David Schwartz Dec 30 '13 at 06:23

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Any decent internet provider will remove that block on a business account. Especially if you are paying for a static IP address, which would be best for running a mail server. Most probably will not remove it on residential accounts.

The blocks are to prevent spam and email viruses spreading. Since the vast majority wont be running their own mail server many ISPs block 25 by default as a safety measure. Of course if you have the block removed and start sending spam, your ISP will be having some words with you.

All you should have to do is call them up and tell them you are running your own mail server. It shouldn't take long or cost anything. If they won't remove the block, take your business elsewhere.

If they won't and you absolutely can't switch ISPs you can setup exchange to use a smarthost/relay, possibly to your ISPs server or to your own VPS somewhere on a nonstandard port. But it is usually best to avoid that and send it directly.

Grant
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