Security News > 2023 > November > Microsoft: Some Outlook.com users can't send emails with attachments
In a Monday advisory, Microsoft warned Outlook.com users about issues they might encounter when sending emails containing attachments.
Outlook.com users impacted by this known issue are seeing "Error code 550 5.7.520 Message blocked" errors when trying to send emails.
"Some users may not be able to send emails that contain attachments from their Outlook.com mailbox," the company said.
In July, Microsoft resolved another known issue triggering 401 exception errors and preventing Outlook.com users from searching their emails.
At the time, impacted users also reported having issues contacting Microsoft 365 support and being caught in a loop of sign-in and Office 365 service choice prompts.
Last year, in October 2022, the company also addressed login issues affecting some Outlook for Microsoft 365 customers using their Outlook.com accounts.
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