my full list of contacts wont upload in BCC when sending or forwarding an email.

Question

my full list of contacts wont upload in BCC when sending or forwarding an email.

ra 0

Recently, when I send larger group emails, the interface has completely changed when I go into the BCC drop down to select recipients in an email I'm forwarding or composing, and the contact list ends at the letter "C". However, when I go to contacts, I can see that my full number of contacts is there. I spoke to someone at Microsoft, and they told me it was a server setting issue and that I should resolve this by online chat, however, when I type in my issue, it says it cant help me. Since I've been having this issue the last couple weeks, not sure if emails are sitting in limbo somewhere, but other email I'm not sending to a group, but to individuals, are not being received, even though from my end I see them, as being sent.

Ryan-N 13,740 Reputation points Microsoft External Staff Moderator

2026-06-12T20:28:46.98+00:00

Hi @ra ,

Welcome to the Microsoft Q&A forum.

To better assist you, could you please help check the following information:

1/ Does the issue also occur when you use the Outlook Web version?

2/ Please try clearing the cache for Outlook to see if the issue with the contact field in BCC is resolved.

To clear the cache for Outlook, you may refer to the documentation below:

Clear the Office cache - Office Add-ins | Microsoft Learn

Additionally, a screenshot would help me better understand and analyze the issue more effectively.

Regarding the case where the recipient does not receive your email while you can see that it has been sent successfully:

In this situation, the issue is likely on the recipient’s side. The fact that you can see the email has been sent indicates that it has already left your mailbox. Please ask the recipient to check whether the email has been mistakenly moved to the Junk/Spam folder, or if there is any rule that automatically moves your email to another folder.

Based on the information you provide, I will be able to assist you more accurately and effectively.

I look forward to your response.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
ra 0 Reputation points

2026-06-12T20:55:05.4266667+00:00

Ive cleared cache as has the Microsoft agent agent who helped trouble shoot remotely. Can an agent please call me back to help? Id prefer not to take pictures of my contact list to post. Im not sure why this agent referred me to the online chat....
Ryan-N 13,740 Reputation points Microsoft External Staff Moderator

2026-06-12T21:02:28.63+00:00

Hi @ra ,

To better assist you, I have sent you a message via private message.

1 answer

Your answer

Ryan-N 13,740 Reputation points Microsoft External Staff Moderator

2026-06-12T20:28:46.98+00:00

Hi @ra ,

Welcome to the Microsoft Q&A forum.

To better assist you, could you please help check the following information:

1/ Does the issue also occur when you use the Outlook Web version?

2/ Please try clearing the cache for Outlook to see if the issue with the contact field in BCC is resolved.

To clear the cache for Outlook, you may refer to the documentation below:

Clear the Office cache - Office Add-ins | Microsoft Learn

Additionally, a screenshot would help me better understand and analyze the issue more effectively.

Regarding the case where the recipient does not receive your email while you can see that it has been sent successfully:

In this situation, the issue is likely on the recipient’s side. The fact that you can see the email has been sent indicates that it has already left your mailbox. Please ask the recipient to check whether the email has been mistakenly moved to the Junk/Spam folder, or if there is any rule that automatically moves your email to another folder.

Based on the information you provide, I will be able to assist you more accurately and effectively.

I look forward to your response.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
ra 0 Reputation points

2026-06-12T20:55:05.4266667+00:00

Ive cleared cache as has the Microsoft agent agent who helped trouble shoot remotely. Can an agent please call me back to help? Id prefer not to take pictures of my contact list to post. Im not sure why this agent referred me to the online chat....
Ryan-N 13,740 Reputation points Microsoft External Staff Moderator

2026-06-12T21:02:28.63+00:00

Hi @ra ,

To better assist you, I have sent you a message via private message.

Answer 1

The behavior described matches two separate issues covered in the context: a limit when using Bcc with many recipients, and general problems sending/receiving mail.

Bcc list appears to stop at “C” / large group emails

When using Outlook in Online mode (not Cached mode) and putting a large number of addresses in the Bcc field, Outlook can have problems displaying or handling the full Bcc list.
This can result in unexpected behavior when composing or reviewing messages with many Bcc recipients.

To mitigate:

Use Cached Mode instead of Online Mode for the Outlook profile.
Use a distribution list (contact group) instead of adding a very large number of individual contacts to Bcc.

If it is necessary to verify who was Bcc’d on a sent message:

Open the message from Sent Items.
On the Other Actions menu, select “Resend This Message”.
Inspect the Bcc field contents.
Close the message without resending.

Some messages not being received For messages to individual recipients that are not being received, common causes include:

Attachment size over 25 MB (message will not send).
Non-delivery reports (NDRs) indicating issues such as invalid address, recipient mailbox full, server issues, or spam filtering.
Low sending quota on a relatively new Outlook.com account.
Signature content occasionally interfering with sending.

Steps to check:

Confirm any attachments are under 25 MB.
If NDRs are received, review the reason in the NDR (invalid address, mailbox full, server issues, spam filters).
If the account is new, review sending limits in Outlook.com.
Temporarily remove the email signature and resend to see if the message is delivered.
Ask recipients to add the sending address to their Safe senders list and/or Contacts.

If problems persist beyond these checks, use the in-product Help in Outlook.com or the provided support entry points to contact support while signed in.

References:

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my full list of contacts wont upload in BCC when sending or forwarding an email.

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