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my exchange server works fine, receiving and sending mail works as expected. now we want to use our barracuda spam firewall as we used it with our old linux mail server. after setting it up, receiving through the firewall works again, all mails get routed correctly. there's one single problem left, receiving:

on our old mailserver i just had to enter the url and the port as mailrelay, without authentication. so i did in my exchange sending connector and adjusted the sending port from 25 to 587 (as described in [1]) via the exchange shell.

the problem is, when i want to send a mail now, i get the following error mail back:

#550 message submission is for authorised users only! ##

this cannot be, because authentication is turned off and the linux server works anyway... as this wasn't clear: i want to send outbound mail through the barracuda!

Sender --> Barracuda --> Recipient

any advice on this issue?

thanks in advance!

[1] http://www.mharder.eu/exchange-2003-2007-2010-smarthost-smtp-port-umstellen/

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Are you trying to get the Barracuda to relay to the Exchange server or are you trying to send outbound through the Barracuda? This isn't clear from your question. –  ewwhite Feb 16 '12 at 20:43
    
sorry: send outbound mail through the barracuda. see edit! thanks –  Tronic Feb 16 '12 at 20:49
1  
Personally, I wouldn't bother. I use Barracuda units for inbound and send directly out from the mail servers. Typically, if you have the need to heavily filter your outbound mail, there are other problems to tackle. –  ewwhite Feb 16 '12 at 20:53
    
i thought about it as secure way to send mails and get rid of spam get sent thorugh our smtp server... –  Tronic Feb 16 '12 at 20:55
    
If you have spam being sent out through your SMTP server, something is definitely wrong with your setup. –  Massimo Feb 16 '12 at 20:59

1 Answer 1

up vote 1 down vote accepted

I don't know how your Barracuda is configured, but usually SMTP on port 25 is used for server-to-server communication, while SMTP on port 587 is used for client-to-server connections, and as such requires authentication.

How is your Linux server configured? Does it connect to the Barracuda using port 25 or 587?

Have you tried configuring Exchange to connect to Barracuda using the default SMTP port (25)?

If instead you actually need to connect to Barracuda on port 587, and Linux can do that without needing authentication, while instead Exchange seems to need it, this may be due to some configuration on Barracuda which allows relay from the Linux server but not from the Exchange one.

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