Max length of MS Exchange Userid

Posted on 2004-08-16
Last Modified: 2010-04-12
My Network Administrator claims that a USERID > 18 bytes "causes trouble" but he does no elaborate.  We use firstname.lastname for USERID and 18 bytes is not long enough for some users.

So my question:  What is the maximum length of an MS Exchange 2000 USERID and where is this documented?

Question by:RockFox
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Accepted Solution

jdeclue earned 125 total points
ID: 11813392
I assume you are referring to the users email address as opposed to the User Account, in Active Directory that a user has to log in to the network and Exchange Servers. Is that correct?

If that is, then the question is "How long can an email address be?"

Here is the answer

Section of RFC 2821 states that the maximum length of any SMTP command is 512 bytes, including the CRLF at the end of the command.

Since an recipient's address is specified by the "RCPT TO:" command:

RCPT TO: <foo@bar.baz>CRLF
So theoretically the maximum length of an SMTP address should be 499 bytes (or characters).


Expert Comment

ID: 11813499
Oh yeah... and if it is the Windows 2000 account, which often has the email associated directly with it, the maximum for AD is 57 characters. I think that is an arbitrary number on Microsoft's behalf.


Author Comment

ID: 11819957
Yes, I'm inquiring on maximum length of a network login name in Active Directory.  I like you answer of 57 bytes.  Can you tell me where it is documented?

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Expert Comment

ID: 11820072
I couldn't find it documented, so I created a user account, opened up ADSI Edit and and made a bogus name, until it wouldn't take any more characters. I then saved the account and logged in with it, to make sure it worked. Then I counted the characters;) Thats why there was 3 minutes between my two posts. Pretty anal, huh!


Author Comment

ID: 11824288
No, that's not anal.  I probably would have done something similar if I had the priviledges.

I was hoping that I could point the Network Administrator to a Micorsoft document.  

I am an IBM mainframe Systems Programmer (VM and VSE for 41 years)  so  of course a M$ admin wouldn't believe me if I told him the time-of-day without  documentation.

Thank you much for you response.


Expert Comment

ID: 11824315
Hah.... I hear ya.. I am a Microsoft guy,.... but I used to work for First Union, spent most of my time working with MQSeries to Unix and Microsoft platforms... spent a lot of time with guys!


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