Why does Outlook emails send multiple times when PDF attachement send with?
Hello,
I think this issue can have several causes, and it often relates to how Outlook interacts with attachments, especially PDFs and the mail server. If the PDF is very large or slightly corrupted, Outlook may fail to complete the "sent" confirmation with the mail server. Outlook then retries sending the email, resulting in duplicates for the recipient.
Then, real-time email scanning from antivirus may interrupt or delay the sending process. If Outlook doesn’t get the confirmation that the message left the Outbox, it may resend the same message multiple times. This happens especially when PDFs are being scanned more thoroughly than plain text emails.
If the email stays in the Outbox after you think it has been sent, Outlook will keep trying to deliver it. This can occur due to poor internet connection, server timeouts, misconfigured SMTP settings, etc. Also, it's important to mention that some Outlook add-ins for PDF handling, signatures, or email archiving may interfere with attachments. These can trigger multiple send attempts if the sending process gets “stuck.”
Or, if your outgoing (SMTP) server takes too long to process attachments, Outlook may assume the attempt failed and retry. The recipient ends up with duplicates once the server processes each attempt.
As it can be noticed, there are multiple reasons, but I think in most cases, the culprit is antivirus email scanning with attachments, or a server timeout with large PDFs. There are a few things to try that can help fix this.
First, make sure to update Outlook and your PDF software (e.g., Adobe Acrobat Reader) to avoid compatibility issues. Then try sending your emails without the PDF attachment. If the issue disappears, the attachment or scanning is the trigger. You can also try to reduce file size or compress the PDF before attaching, although this shouldn't really be required.. Also perhaps you could run Outlook in Safe Mode (outlook.exe /safe) to see if an add-in is causing it? Finally, disable the antivirus shield temporarily and test again.
I hope this helps.
Regards
