Apparently my Outlook is trying to send out thousands of erroneous emails that I didn't create, and I cannot find where they are coming from.

How do I stop them?

Hi,

What type of account are you using? Exchange, POP or IMAP?

Please exit Outlook, then logon OWA/Webmail, check if the issue persists. In my opinion, this issue can be caused if your account is hijacked, contact your Email service provider and check the recent logon details, you may consider to change your password too.

We can also start Outlook in Safe Mode to determine whether 3rd-party add-ins can be the culprit:

Press Win + R, type "outlook.exe /safe" in the blank box, press Enter.

If there is no such issue in Safe Mode, disable the suspicious add-ins to verify which one caused the issue.

Regards,

Melon Chen
TechNet Community Su

Apparently my Outlook is trying to send out thousands of erroneous emails that I didn't create, and I cannot find where they are coming from.

How do I stop them?

Just to cover all bases - when you say "apparently my Outlook is trying...." - what exactly do you mean by the word "apparently"? How are you determining that in fact Outlook is "sending" these emails or are you getting a lot of "bounce back" messages that "appear" to be coming from you and assuming that it was your system that actually sent those to begin with? Not uncommon for spammers to hi-jack an email address, blast emails to hundred's of thousands of recipients resulting in "bounce-back" messages from the receiving server back to your email address.