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i'm having a very strange problem - there's a client running outlook 2003 with 2 email accounts. they're configured exactly the same (except username/password), they both have "authentication-on-send" enabled.

the weird thing: one account can send, the other won't. i checked the logs and found out that one account is sending EHLO (which let's him send), the other account is just sending HELO (which won't relay).

i couldn't find out the reason for that HELO/EHLO difference :/

i tried anything - deleting/re-creating that account, didnt work. even on a different machine, same problem.

the lan runs over a AVM Ken proxyserver. i've also tried deleting/re-creating the account - no success.

any ideas what could be wrong?

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up vote 1 down vote accepted

Do either have antivirus that might be intercepting the connection? I vaguely recall AVG amongst others did something like this (although this was from a long time ago).

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as i said, the strange thing is i have both accounts on the same machine/same outlook! one uses EHLO (works), the other HELO (doesn't). when directly mailing out to the mailserver, it works! – Fuxi Dec 2 '09 at 22:08
Ah, sorry - had to re-read it as it sounds so bizarre. Did you see the HELO in server or client logs? If server then perhaps try enabling transport logging in Outlook ( to narrow down the source of your woes? – SimonJ Dec 2 '09 at 22:42
thanks for your help - i'll try enabling the log. i'm having an assumption that the proxy has listed that account twice/wrong - and trying to relay locally (without auth). need to find it out somehow .. – Fuxi Dec 3 '09 at 11:09

The difference in the request is HELO is an older form of EHLO. EHLO is basically asking if it the server can handle more advanced SMTP commands (such as check attachment size, and other functions I can't think of now).

So there are 2 issues, one is why is one client asking for an enhanced connection and the other is not.

The other is why isn't the EHLO accepted by your mail server. It should accept either query.

Not an answer for you, but my 2 cents.

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The poster said that EHLO does allow him to send. It's only when Outlook greets the server with HELO that it rejects the mail - reason being that one of those "other functions" is SMTP AUTH ;) – SimonJ Dec 2 '09 at 22:49

Have you verified that your encryption (TLS/SSL) settings are configured the same?

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Didn't SimonJ give you the answer in his comment? SMTP authentication isn't available with the HELO command set, right?

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But the question is, why is Outlook sending HELO for one of the accounts (despite being configured to use authentication, which mandates use of EHLO)? Either that or something else is intercepting the connection and "downgrading" it. – SimonJ Dec 3 '09 at 0:56
Right, good point. – joeqwerty Dec 3 '09 at 2:13

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