[2024-feb-29] Sad news: Eric Layton aka Nocturnal Slacker aka vtel57 passed away on Feb 26th, shortly after hospitalization. He was one of our Wiki's most prominent admins. He will be missed.
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
howtos:misc:proxying_smpt [2015/11/27 23:19 (UTC)] – [Scenario 3] louigi600 | howtos:misc:proxying_smpt [2016/04/28 07:34 (UTC)] – [Proxying Emails to Your Local Mail Relay Server] louigi600 | ||
---|---|---|---|
Line 6: | Line 6: | ||
Here are some scenarios with examples on how you could go about working around the problem. | Here are some scenarios with examples on how you could go about working around the problem. | ||
- | Throughout the scenarios we will be referring | + | Throughout the scenarios we will be referring |
- | * Machine A with IP address 192.168.0.2 (cannot send meils directly via internet and cannot | + | * Machine A with IP address 192.168.0.2 (cannot send mails directly via internet and cannot |
* Machine B with IP address 192.168.1.2 | * Machine B with IP address 192.168.1.2 | ||
* Local Mail Relay (LMR) with IP address 192.168.2.2 | * Local Mail Relay (LMR) with IP address 192.168.2.2 | ||
Line 14: | Line 14: | ||
===== Scenario 1 ===== | ===== Scenario 1 ===== | ||
- | Machine A cannot | + | * Machine A cannot |
- | but Machine A has access to machine | + | |
+ | * Machine B can relay thought LMR | ||
+ | * Machine B can reach LMR's port 25 | ||
- | We can use nc to proxy mail from A to LMR | + | We can use nc on Machine B to proxy mail from A to LMR. In this example it will appear to LMR as if it was Machine B that is sending the email. |
On machine B | On machine B | ||
Line 53: | Line 55: | ||
===== Scenario 2 ===== | ===== Scenario 2 ===== | ||
- | Let' | + | * Machine A cannot reach LMR' |
- | can we use a ssh tunnel between A and LMR to do the job for us ? | + | * Machine A is allowed to relay thought LMR but firewall is preventing it from reaching port 25 on LMR |
+ | * Machine A can reach the LMR but only on port 22. | ||
+ | |||
+ | We use a ssh tunnel between A and LMR to do the job for us. In this example we are bypassing firewall by using ssh to forward traffic trough a encrypted tunnel. For this to work properly the ssh client that is going to be forwarding needs to be executed by an administrative account. | ||
<note important> | <note important> | ||
Line 80: | Line 85: | ||
- | + | ===== Scenario 3 ===== | |
- | This method may or may not work depending on whether MTA on LMR is configured to allow Machine A to relay trought it. This leads to yet another scenario (see Scenario 3) or an alternative method provided the following conditions are met: | + | |
* Machine B can relay emails trough LMR | * Machine B can relay emails trough LMR | ||
+ | * Machine B cannot reach LMR's port 25 | ||
+ | * Machine B can access LMR via ssh | ||
* Machine A has access to Machine B on whatever port we choose to let ssh listen on for forwarding (1024 in the exaple). | * Machine A has access to Machine B on whatever port we choose to let ssh listen on for forwarding (1024 in the exaple). | ||
Line 89: | Line 95: | ||
We can then start the ssh socks proxy on Machine B listening on a port Machine A can access: | We can then start the ssh socks proxy on Machine B listening on a port Machine A can access: | ||
- | On machine B | + | On machine B with a privileged user |
ssh -2 -D 192.168.1.2: | ssh -2 -D 192.168.1.2: | ||
Line 115: | Line 121: | ||
===== Scenario 4 ===== | ===== Scenario 4 ===== | ||
- | Mostly like Scenario 2 but Machine A is not allowed to relay on LMR dew to MTA configuration. | + | * Machine A cannot reach LMR's port 25 |
+ | * Machine A is not allowed to relay thought | ||
+ | * Machine A cannot proxy on any other machine that is allowed | ||
+ | * Machine A can reach the LMR but only on port 22. | ||
We can still get the whole command to run on the LMR via ssh: | We can still get the whole command to run on the LMR via ssh: | ||
+ | |||
+ | <note important> | ||
cat << EOF > send_this_mail | cat << EOF > send_this_mail |