VirMach is not affiliated with Microsoft/Outlook/Hotmail. This is our opinion/interpretation of their policies.
Not receiving emails from VirMach:
If you do not receive e-mails from us and you are using Outlook/Hotmail or other related services, such as a business e-mail that uses their services, it is highly likely that Outlook is blocking our e-mails from ever reaching your inbox or spam folder. Unfortunately, there is no solution to this from our end. We recommend using another e-mail provider that does not actively filter out e-mails before it reaches your inbox (and thus allowing you to set your own filtering rules.)
Cannot send emails to Outllok:
This issue also occurs if you have a service with us and you are attempting to send an e-mail to Outlook-controlled mailservers. Your emails may be blocked. We cannot assist you with this matter, but if you do provide a link to a public e-mail blacklist where we can quickly identify  why an IP is blocked,  how it can be de-listed, and  where we can look up other IP addresses then we can change this IP address for you per our terms of service (within 24 hours) or you can request a custom IP change and list this as one of your requirements (that it be checked against that specific list.) As of writing this help article, Outlook/Hotmail may either block emails entirely without much explanation or may send a response requesting that you complete a captcha to continue sending emails.
1. Example of error blocking e-mails arbitrarily:
hotmail-com.olc.protection.outlook.com[<Hotmail Server's IP>] said: 550 5.7.1
Unfortunately, messages from [<Your Service's IP>] weren't sent. Please contact
your Internet service provider since part of their network is on our block
list (S3140). You can also refer your provider to
If you receive this message, there is unfortunately nothing we can do because Hotmail/Outlook does not provide a proper public blacklist where we can look up the IP address and see why it's blocked and request an unblocking.
2. Example of error requiring captcha/throttling:
Server response: 550 5.7.606 Access denied, banned sending IP [<Your Service's IP>]. To request removal from this list please visit https://sender.office.com/ and follow the directions. For more information please go to http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609) [QB1CAN01FT007.eop-CAN01.prod.protection.outlook.com]
If you receive this message, you need to use the delisting portal to remove your IP from the list. Usually this involves filling out a form, and completing a captcha.