Mail Merge - some messages does not reach their destination, no error messages

Question

Mail Merge - some messages does not reach their destination, no error messages

Jane3 0

Some messages sent via Word Mail Merge fail to reach the recipient, even though everything indicates that they have been sent. The messages appear in the sender's "Sent Items" folder, and no error messages are generated. Personal information from an Excel spreadsheet is merged into each message. I do not know exactly who or how many of the approximately 250 recipients are not receiving their messages, but I have received a few reports from people stating that they did not receive a message they were waiting for. Furthermore, the messages do not end up in the recipients' junk/spam folders. There does not appear to be any pattern regarding the email address domains. I have also tried sending the message to each person on the recipient list individually—still using Mail Merge, and sending them as quickly as possible, one after another—yet one recipient is complaining that they did not receive the expected message. And if that’s the case, there could easily be others. As long as it behaves this way, the feature is completely useless. The least one expects is an error message. Is this a known issue, and is there a solution for it? I am using the latest version of MS 365 and classic Outlook.

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Emma1-N 15,245 Microsoft External Staff Moderator

Welcome Jane3,

Thank you for providing such a detailed explanation. I understand your concern, especially when some recipients do not receive important messages even though the messages appear in your Sent Items folder.

Word Mail Merge sends an individual email to each recipient through a MAPI-compatible email application, such as Classic Outlook. However, seeing a message in Sent Items does not necessarily confirm that it has successfully reached the recipient’s mailbox. Microsoft’s documentation on this feature: Use mail merge in Word to send bulk email messages

Before proceeding, could you please clarify a few things?

Which email account are you using as the sender in Classic Outlook? Is it a personal Outlook.com/Hotmail account, Gmail, or another email provider?
When you send a regular email directly from Classic Outlook to one of the affected recipients (without using Word Mail Merge), does the recipient receive it successfully?
Have you noticed whether the affected messages remain in the Outbox temporarily before appearing in Sent Items, or do they move to Sent Items immediately?

In the meantime, I suggest trying this simple test:

Open Classic Outlook and compose a new email manually.
Send a test message to one recipient who previously reported not receiving your mail merge message.
Check whether the recipient receives this message and whether you receive any delivery failure notification from the postmaster.

Additionally, Outlook supports delivery receipts for individual messages. You can request one from the message’s “Options” tab by selecting “Request a Delivery Receipt”. Keep in mind that receipt availability depends on the recipient’s email system.

I look forward to your response.

Emma1-N 15,245 Reputation points Microsoft External Staff Moderator

2026-11-14T07:59:27.76+00:00

Hello Jane3,

I just wanted to check if my previous response addressed your question correctly. If there is anything I may have misunderstood, I would truly appreciate it if you could provide a bit more detail to help me better understand your needs.
Jane3 0 Reputation points

2026-11-14T15:11:20.64+00:00
Thanks for a prompt response!

The email account I'm using as a sender is a private outlook.com-account.

A regular email without using Word Mail Merge directly to one of the affected recipients is received successfully.

I do not know whether the affected messages remain in the Outbox temporarily before appearing in Sent Items.

I have now turned on request for delivery receipts from recipients email servers and tested it by sending a regular mail to a couple of addresses - a @online.no address and a @gmail.com address. The recipients confirm that message is received, but I do not get delivery receipts from any of their servers.

I have also tried to send a single message merging data from an Excel sheet using Mailings again, to one of the earlier affected recipients. The message is confirmed as received.

Has Microsoft any limits on the number of recipients in the use of Mailings for private accounts in order to reduce the spread of spam? Should in that case have been clearly documented or at least triggered a warning. Or can it be related to a capacity problem leading to some messages being skipped. There are about 250 in the recipients list filtered from an Excel spreadsheet with about 4000 rows.