Outlook Classic not sending PDF files in group email

Question

Outlook Classic not sending PDF files in group email

Grace Community Church 0

Been using Outlook Classic to send all emails for over 2 years. Suddenly it has decided to not send attachments, send an 'outlook file', or send attachments that nobody can open. Suggestions? Have tried everything found online, nothing has helped.

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Answer 1

Hi Grace,

As a forum moderator, I am not able to access your account or delve into the backend systems to diagnose and fix this for you. My role here is limited to providing general guidance and solutions for users to implement themselves. What you are describing, particularly the attachment arriving as an "Outlook file," usually points to the message being sent in Rich Text Format. When that happens, Outlook bundles attachments into a winmail.dat file that recipients outside Outlook cannot open. To confirm the format is the cause, please follow these steps:

Go to File > Options > Mail, and under Compose messages in this format, select HTML.
Start a completely new message. Do not reuse or forward an older one.
On the Format Text tab, confirm HTML is selected.
Attach one small PDF and send it to a single affected recipient.

If that fixes it for one recipient but the group still fails, delete the group and the individual addresses from Outlook's autocomplete list by typing the name, then clicking the X next to the suggestion, and retype the address fresh. Outlook stores per recipient format settings there, and a saved RTF preference will override your global setting.

If the format change does not help, I recommend that the Global Admin in your organization create a service request with Microsoft Support. A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin. If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support

For additional assistance, use this link to find the appropriate contact number from your region: Contact Microsoft customer support | Microsoft Support

I truly hope you get your issue resolved swiftly. Please know that even though I can't directly intervene, directing you to the correct, specialized support is the most effective help I can provide from my position. Thank you for your patience and understanding. Please let me know if you need anything else. Wishing you all the best.

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Grace Community Church 0 Reputation points

2026-09-22T14:21:06.75+00:00

Thanks for replying. I've tried all the "fixes" such as changing the format. I've tried rich text, plain text and HTML. I was using HTML for years and sending multiple PDF's to multiple recipients with no problems. This just started. I have my email in the group and when I get the emails, sometimes they have the outlook file attachment, and I can open that. Other times, I get the PDF's.
Kai-L 20,030 Reputation points Microsoft External Staff Moderator

2026-09-22T21:22:45.6433333+00:00

Hi Grace,

Thank you for the update, that helps narrow things down. Since you have already tested every message format and the behavior still varies from one send to the next, this goes beyond what can be worked through from the forum side. At this point I would recommend having your Global Administrator raise a service request with Microsoft Support so they can investigate directly. The steps for that are in my previous reply. Do let me know how you get on once support has taken a look.