Not receiving <InReplyTo> tag in EWS GetItem response if mail subject changed in reply

Question

Not receiving <InReplyTo> tag in EWS GetItem response if mail subject changed in reply

Raghunandan Kumbhar 20

I have an add-in that I run in Exchange Server 2019. When replying to an email, my add-in requires some information related to the parent email. For this, I use the EWS GetItem API. In the response, I get an <InReplyTo> tag, where I find information about the parent email.

See below example for more info:

User's image

The issue is that if I change the subject in the reply, I do not get that <InReplyTo> tag in the response, and hence cannot access parent email information.

This issue is only observed in Outlook on Mac (classic UI).

Any information, workaround, or timelines on a potential fix for this issue will be greatly appreciated.

Do let me know if any further information is required from my end.

1 answer

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Answer 1

Hin-V 2,075 Microsoft External Staff Moderator

Hi @Raghunandan Kumbhar

Thank you for posting your question in Microsoft Q&A.

Based on your description, I understand you have considered to receiving <InReplyTo> tag

in EWS GetItem response in Outlook on Mac. We are glad to assist you this part.

From my perspective, this might be a platform-specific behavior (or potential bug) in Outlook on Mac. When the subject is changed during a reply, Outlook might intentionally or inadvertently omit the In-Reply-To header from the draft item to signal the start of a new conversation thread. This header is what populates the <InReplyTo> element in the EWS GetItem response. Standard email protocols don't require removing it, but client implementations like Outlook can vary.

The <InReplyTo> element corresponds to the first-class property with FieldURI item:InReplyTo, which is typically populated with the original message's ID for replies.learn.microsoft.com.

To confirm you're requesting it correctly in your GetItem call, ensure your XML includes it in the <AdditionalProperties> section include (it's not returned by default in the base shape):

<GetItem xmlns="
  <ItemShape> 
    <BaseShape>IdOnly</BaseShape> 
    <AdditionalProperties> 
      <FieldURI FieldURI="item:InReplyTo" /> 
      <!-- Add other properties as needed, e.g., item:ConversationId --> 
    </AdditionalProperties> 
  </ItemShape> 
  <ItemIds> 
    <ItemId Id="your-reply-item-id" /> 
  </ItemIds> 
</GetItem>

If <InReplyTo> is still missing despite this, it's likely due to the client not setting the header.

I have found relevant article that might help:

Properties and extended properties in EWS in Exchange | Microsoft Learn

Work with Exchange mailbox items by using EWS in Exchange | Microsoft Learn

InReplyTo | Microsoft Learn

Please let us know if you need further assistance.

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Raghunandan Kumbhar 20 Reputation points

2025-07-23T06:41:20.23+00:00

We have already tried this, we still do not get the <InReplyTo> tag in the response. Is there anything else that we can try?
Hin-V 2,075 Reputation points Microsoft External Staff Moderator

2025-07-25T13:36:35.0133333+00:00

Hi @Raghunandan Kumbhar

Sorry for my delayed response.

This might be a platform-specific behavior (or potential bug) in Outlook on Mac. I’ve tried searching and reading related documentation, but I haven’t found a specific method for troubleshooting on the Mac client yet.

To resolve this issue quickly and effectively, I recommend reaching out directly to the Microsoft Tech Community. They are best equipped to address and troubleshoot this type of problem. As a forum moderator, I don’t have access to detailed information regarding the limitations or potential issues you might encounter when running this command.

Apologies for redirecting you to the related development team support, as the moderators in this community have limited resources to check this information, and to get the fast and better assistance we requested for it.

Appreciate your patience and understanding.

Warm thanks and have a nice day.
Hin-V 2,075 Reputation points Microsoft External Staff Moderator

2025-07-28T07:07:10.06+00:00

Hi @Raghunandan Kumbhar

I hope you are doing well.

Have you had a chance to check the replies provided?

Any update would be appreciated.
Hin-V 2,075 Reputation points Microsoft External Staff Moderator

2025-07-30T06:59:14.1+00:00

Hi @Raghunandan Kumbhar

Just checking in to see if the above information was helpful.

If you have any further updates on this issue, please feel free to post back.

Any update would be appreciated.

Warm thanks.
Raghunandan Kumbhar 20 Reputation points

2025-08-07T13:06:02.42+00:00

Thanks for all the prompt responses.

The issue has not been resolved yet. I will head to the Tech Community Forum to check for any fixes.

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Not receiving <InReplyTo> tag in EWS GetItem response if mail subject changed in reply

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