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How do I unblock the port 25 in my mac firewall?

Posted on 2008-06-12
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Last Modified: 2013-11-12
How do i unblock the port 25 in my mac firewall? I cannot use my mail client such Mail or Entourage. I did
telnet mailserver 25 and got "connection refused".
On the other hand, I can receive mail because the incoming mail port 993 is opened, I did
telnet mailserver 993 and was able to get through.
I can use Outlook on my Windows to send mail.
So I reckon the port 25 must have been blocked by my mac.
Thanks!
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Question by:michaelzhou23
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by:Jascot
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This isn't a Mac answer for you, but you may wish to check with your ISP, especially if you are using a mail server other than your ISP's mail server. Many ISPs are now blocking outgoing connections to port 25 as a way to try to cut down on spam being sent by virused Windows PCs. If you are not using your ISP's mail server, then see if your mail server supports sending via port 587 or port 465 with SSL. Those are alternate ports which many mail servers allow for sending emails.
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by:kanlue
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can you double check the outgoing server settings in your outlook since you are able to send out email there? which outgoing server is using? which port is using?

hope it helps.
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by:michaelzhou23
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No, my ISP is not blocking port 25. I just phoned them. Additionally, I can use outlook to send mails on my Windows, so port 25 must be open at least in ISP.
I used exactly the same setting as the one I am using for Outlook on Windows.
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by:kanlue
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about leopard firewall settings, heres a few tips:

open terminal;

to add a port:
sudo ipfw add allow [udp or tcp] from [port] to [port]
So, if you want allow port 25 with tcp youd type sudo ipfw add allow tcp from 25 to 25

to see your rules:
sudo ipfw list

to delete an open port:
first type sudo ipfw list, youll get something like this

65535 allow ip from any to any

take the number proceeding the rule you want to delete and type sudo ipfw deletem [rule number], so if I wanted to delete the rule 33500 allow tcp from 0.0.0.80 to 0.0.0.803 Id just type
sudo ipfw delete 65535


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by:michaelzhou23
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And using 587 or 465 with SSL does not work either. Anyhow, down to my initial question, is it possible that my Mac firewall blocks port 25?

Thanks!
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by:michaelzhou23
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thanks i will try adding the port!
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by:michaelzhou23
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Hi,
  I tried adding the port as "sudo ipfw add allow tcp from 25 to 25" but still no luck.
  I did notice one thing though: when i telnet mailserver 25, after a short while it displays:
telnet: connect to address 74.85.6.10: Connection refused
telnet: Unable to connect to remote host
  However, if I telnet other meaningless ports such telnet mailserver 888, it is trying to connect infinitely.
  So I guess either the system must know something special about port 25?
  Thanks!
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kanlue earned 125 total points
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i don't think that your mac blocks the port.

let's do more test here: did you try 'telnet smtp.gmail.com 25'?
-----------------
telnet smtp.google.com 25
Trying 209.85.237.25...
Connected to smtp1.google.com.
Escape character is '^]'.
220 smtp.google.com ESMTP
quit
221 2.0.0 smtp.google.com closing connection
Connection closed by foreign host.
------------------
(i did it in my mac and i got the reply.)

if you can get the reply, then i would suggest you delete the outgoing server settings in your apple mail, then create it again.

by the way, i did not change my firewall settings, when i did a test to 'telnet 74.85.6.10 25' and i got reply in my mac.

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by:michaelzhou23
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Hi kanule,
  I think we may get closer.
  I tried telneting to gmail smtp and got rejected as well:
********************
telnet smtp.gmail.com 25
Trying 209.85.201.109...
telnet: connect to address 209.85.201.109: Connection refused
Trying 209.85.201.111...
telnet: connect to address 209.85.201.111: Connection refused
telnet: Unable to connect to remote host
**********************
  On the other hand, I can telnet to port 25 on any mail server from my windows machine, in the same network.
  So logically, I don't see any other reason than that Mac is blocking port 25.
  Thanks!
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by:michaelzhou23
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Hi kanlue,
  I've managed to send mails finally. The ISP blocked the port 25 and I asked them to turn it on for me so I get through now.
  However, one thing confuses me infinitely though, even before they turn it on for me, why was I able to send mails on my Outlook on Windows platform? I have been doing that for 2 years! Only until the last week that i bought my Mac. Does the ISP even know which operating system you are using? That's a wicked phenomenon.
  Thanks!
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by:kanlue
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hi michaelzhou23, do you need to connect to vpn before you open the outlook?
and also who is your ISP? just curiosity.

thanks for the update, and glad that you have it fixed.
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by:michaelzhou23
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No, I did not need to VPN when I was using Outlook on Windows, the time when the smtp port (25) was blocked by my ISP. I'm using Australia's optus.
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