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Setting up a CentOS VM for an SMTP server - Page 2

post #11 of 16
Thread Starter 
My workstation uses Windows 7 Pro, bare metal.
The other server I just tested the connection from is a Windows Server 2008 R2 VM. I believe it's the same Telnet client between Windows 7 and 2008 R2 smile.gif

P.S. I actually used PuTTY on the Windows Server box, but I'm getting the same result on my Win7 box whether I'm using Windows' Telnet client or PuTTY.
post #12 of 16
Thread Starter 
For everyone's edification, the issue is resolved. It wasn't a Postfix configuration issue or anything to do with the Telnet clients or OS I was using. Instead it was a setting on a Cisco firewall sitting between my workstation and the SMTP server which was inspecting ESMTP traffic (coincidentally it's called "inspect esmtp"). Disabling the setting fixed the issue immediately.
post #13 of 16
Quote:
Originally Posted by Shub View Post

For everyone's edification, the issue is resolved. It wasn't a Postfix configuration issue or anything to do with the Telnet clients or OS I was using. Instead it was a setting on a Cisco firewall sitting between my workstation and the SMTP server which was inspecting ESMTP traffic (coincidentally it's called "inspect esmtp"). Disabling the setting fixed the issue immediately.

Hahaha I bet that was I pig to find.

Thanks for the update by the way
post #14 of 16
Thread Starter 
I only take credit for finding the root cause in that I spent two days testing everything I possibly could from a configuration standpoint =P
I even set up a Windows Server 2008 R2 VM to see if it would give me the same problem, and it did, so at that point I knew it had something to do with my network, so I spoke to a network engineer. I kind of steered him in the right direction but he immediately found the issue.
post #15 of 16
Glad you found the fix. I suspected it was a "protocol error" or "encoding error", which is why I suggested spinning up a Linux VM. It would have eliminated or blamed the Windows telnet client as the culprit (which was wrong anyway tongue.gif). I never thought an "intelligent" router would be the problem, lol. biggrin.gif
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post #16 of 16
Quote:
Originally Posted by Plan9 View Post

sendmail configuration is like black magic. It's a complete nightmare. Postfix retains a lot of compatibility but wraps it up with a lot saner config files.
[edit]
Oh. sorry, forgot about hardware. Basically it doesn't look as if you're accounting for attachments. Base64 encoding adds about 30% to attachment file size (SMTP really is that crap!) so double your RAM and your disk space just to give you some buffer for encoding/decoding base64.
Also, give yourself a 2GB swap space. You shouldn't need it but the last thing you need is out of memory exceptions as that could result in lost mail.

I can't say I ever encountered a huge issue setting up sendmail for a SMTP relay for work. But my setup is really simple. Receive from other servers, forward to next SMTP via MX record lookup. The only difficult part was making it realize my allowed relay list. And honestly it wasn't too much work. But I over went on the server with storage. We have 100 GB in the /var partition, but it's small, 1 vCPU and 1 GB ram in VMWare.
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