We’ve seen a sharp rise in the last couple of days of instances where clients using their VPS with us to send mail, cant send to people who have Hotmail/Microsoft based email addresses.
If you’re being blocked by them, you’ll get something along the lines of the following as a bounce back:
<firstname.lastname@example.org>: host mx3.hotmail.com[126.96.36.199] said: 550 SC-001 (BAY004-MC4F51) Unfortunately, messages from 188.8.131.52 (your IP address) weren’t sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command)
There are a number of reasons this can happen, your server could be sending out spam email through a compromised email account or site, recipients of email from your server who use Microsoft may have marked messages from yourselves as spam, or there might not be an SPF record in place for Microsoft to verify your domain is permitted to send email from your server.
1 – Check your server is not sending out spam through a compromised site/mailbox. In Plesk you can check the mail log for issues by going to Tools & Settings -> Mail Server Settings -> Mail Queue (Tab). In cPanel you can check the mail log in Home -> Email -> Mail Delivery Reports. If theres lots of suspicious looking mail items in the list, it’s likely you have an issue. You can check the Plesk mail log on the command line in /usr/local/psa/var/log/maillog or cPanel in /var/log/exim_mainlog. Contact Nimbus Support if you believe this is the case and we’ll do some investigation for you to see if we can pin down where it is coming from.
2 – Make sure no one is using your server for mass marketing email. Again have a look at the mail log – it’s likely there will be some entries in there for non delivery to old/incorrect email addresses if it is being used heavily for mail. If there is someone doing so, recommend they use someone like the fantastic Mailchimp for mass mailing.
3 – Ensure the domain you are sending from has an SPF record to identify the server IP as an authorised sender. If you’re using our Nameservers for your domain, we have a handy tool you can use: Check out this SPF blog post for more info.
Once you’ve checked your mail log, made sure you have an SPF record, and are fairly sure no one is using your server to send out mass marketing emails, fill out this form to request to be delisted:
Finally, we’d definitely recommend moving your email to Google Apps or Office 365, or the FREE Zoho. As these platforms move your mail away from your web hosting, your mail is sent from a range of the providers IP’s – meaning that issues like the above should be a thing of the past. Have a read of this blog post on why we recommend them; it’s where most people are heading for their mail these days.