Thursday, May 10, 2007

Error 500 Non RFC-Compliant responses received; there was a SMTP communication problem with the recipient's email server

Please take a look at below article explaining why this error has occurred, and how to prevent it happening in the future.

Author: Oz Ozugurlu

Error: 500 Non RFC-Compliant responses received; there was a SMTP communication problem with the recipient's email server. Please contact your system administrator. < #5.5.0 SMTP; 500 Non RFC-compliant response received>

Multiple SMTP addresses bounce back to the sender, along with the error above

Cause: Client copied and paste several SMTP addresses into outlook. These SMTP addresses are taken from access database, or some other database application such as Microsoft word, excel, or Client has local distribution list created on his or her outlook.

The Distribution list is a Local list. There is a Bad address among these contact addresses, most of the time it is a space

Or misspelled, completed with illegal character such as news@ (Space) or _


In order to alleviate the problem, try to send mail to each mail address individually. The mail won't bounce and it will go through, because the extra space issue will be eliminated by this way.


Exchange is %percent RFC compliant product.

When Client is copying and pasting SMTP addresses into outlook, outlook application seems to be putting extra space, between multiple E-mail addresses, therefore mail is bouncing. To prevent this being happen, space must be eliminated. Based on experience this error is most likely Occurred on Outlook 2002 platform and there are no errors on the server side.


This is the easiest, (work around) way to get away with this error, Break the E-mail messages into smaller groups and try it again. This will prevent the space issues within outlook (Smaller groups) and message will go through.

Open your contacts and make sure there is not space or illegal characters or corrupted SMTP address in it. After making corrections try to send mail one more time

Most of the time client will say, this used to work in the past, why all of a sudden it is not working. The corruption on local DL probably did not existed in the past, when e-mail was sent to this local DL.

Permanent solution would be

• Create a DL (distribution List) on AD (active Directory)

• Create External Contacts for each SMTP address,

• Add all the External Contacts to this DL as a member.

Try to make use Microsoft word is selected as a word editor and also within outlook by going

  • Tools
  • Options
  • E-mail options
  • Advance E-mail Options
  • Allow Comma as address separator
  • Make sure it is selected

Oz Ozugurlu

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