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CCericola_13974's avatar
CCericola_13974
Icon for Nimbostratus rankNimbostratus
Nov 22, 2009

SMTP Load Balanciing - strange behaviour

I'm sure I'm missing something simple, but we're trying to load-balance SMTP across a few IIS SMTP servers. I've setup the pool, the SMTP monitor, and the virtual server.

 

 

The pool is showing the servers as active. Relaying and access is enabled for the BigIP for the mailservers.

 

 

The virtual server is configured for port 25 and is using the tcp-lan-optimized profile for both server and client. Everything else is left at the default except SNAT Pool which is set to "Auto Map".

 

 

If I try to send a mail from my local machine using telnet, I always get "500 5.3.3 Unrecognized command" regardless of which command I send.

 

 

Am I missing something simple?
config
design

2 Replies

  • bruce__12158's avatar
    bruce__12158
    Icon for Nimbostratus rankNimbostratus
    Nov 22, 2009
    Looks like you are talking successfully to an SMTP daemon. Can you see the traffic flowing via "bigtop -n" or through tcpdump?

     

     

    Here's the basic code to send a manually crafted email. Some mail servers will enforce the angle brackets around addresses, and some will enforce proper host declarations during the ehlo/helo statement.

     

     

     
 telnet a.b.c.d 25 
 helo some.host 
 mail from:  
 rcpt to:  
 data: 
 subject: subject line 
 message text goes here 
 . 
 quit

     

     

  • CCericola_13974's avatar
    CCericola_13974
    Icon for Nimbostratus rankNimbostratus
    Nov 23, 2009
    I think I've found the issue, but I'll confirm tonight. But long story short, there seems to be something that's messing up the connection when I was testing from our VPN. Once I'm on the network, there's no issue.