Exchange 2010 + Outlook 2007. Users send outlook meeting request to a list of recipients both interanlly and externally to the organisation. Some recipients report receiving 'garbled' messages instead of meeting requests.

The emails received by some external recipients show emails with base-64 encoded attachments - and they are not able to add the meeting request to their calendar or even view it. Example of received email below:

Accept-Language: en-US, en-NZ
Content-Language: en-US
acceptlanguage: en-US, en-NZ
Content-Type: multipart/alternative;

MIME-Version: 1.0
X-OriginalArrivalTime: 15 Jul 2011 03:15:21.0709 (UTC)

Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64


Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: base64


Content-Type: text/calendar; charset="utf-8"; method=REQUEST
Content-Transfer-Encoding: base64



I've shortened the base 64 encoding blocks in the above sample, but I can confirm that I've manully re-encoded the base 64 and they convert appropriately to a plain text version of the request, an HTMl version, and an .ics file which opens fine in outlook (2010).

These particular recipients normally get meeting requests fine, but something seems to be causing a probles with some of these requests.

The external recipients report using 'Outlook', but at this stage we can't be sure if it is Outlook, or Outlook Express or which specific versions.

Searching google, some bug reports for Thunderbird describe the client not re-encoding attachments, but none of our recipients seem to be using Thunderbird. There also appears to be some discussion about Outlook 2000 not opening .ics files - however , the recipients can't even see the attachments as such - but rather just encoded base 64 MIME.

Please help!

1 Answer 1


We had a similar issue with Exchange 2007 + outlook 2007. calendar invites sent from outlook express by client once received and accepted, the response which was sent back, the user found the response as above.

We had raised a ticket with MS and they confirmed it is a bug is Exchange 2007 and outlook express client.

Not sure abt Exchange 2010 whether they have fix this issue

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.