Email sending not working in Mailgun to Outlook

Question

I'm using mailgun API for sending emails to the user accounts. I keep checking the mailgun log for checking the send statuses. My problem is everything is working fine when sending emails to gmail and yahoo. It is not working for hotmail. I have checked the junk folder in hotmail. I couldn't find the email. Here is the mailgun log for the delivered status to hotmail email account.

02/24/14 04:44 AM Delivered: [email protected] → [email protected] 'Welcome! Outlook Test'

Please help me to resolve this. Thanks in advance.

Answer 1

Although it seems as if it is delivered, in fact it was blocked by hotmail. You should check your Bounce tab in mailgun but you probably won't find anything there too.

Take the following steps to try to narrow the causes:

• Check the headers of a delivered email to see what mailgun server it was sent from.
• Get this IP and search it for blacklisting. Especially in http://www.spamcannibal.org/
• Lookup the same IP at SendScore.

Now, assuming that you don't have a dedicated IP from Mailgun, you'll notice that your IP might not be blacklisted but several other IPs from the same range might be. This is enough for hotmail to block your emails without giving you a reason.

Ask Mailgun to move you to a different IP and hope that a bad internet marketeer won't be using it too.

Hope this helps Theodore

Answer 2

While the above answer does have a few helpful hints, it is inaccurate in a few respects.

First, Hotmail does not block emails based on a SpamCannibal listing. Hotmail's own IP's are listed with this blacklist as well as the IP's of every other major ESP. Second, the reason that the IP's are listed with SpamCannibal is that they are a blacklisting service that extorts payment in return for being delisted. Of course, once delisted, nothing stops SpamCannibal from placing the IP - or an entire subnet - back on the listing. Third, no reputable ESP uses SpamCannibal in their filtering decisions. Fourth, the only known service that relies on SpamCannibal is the obscure Linux spam filter Linux Magic, and that's only because that service does a lookup of the blacklists on MX Toolbox.

All in all, being listed on SpamCannibal will not affect email delivery, regardless of whatever email service you use. If you're being blocked by Hotmail, it could be due to your domain's reputation, your IP's reputation, or your email content (usually the last option). To see Hotmail's email policies, visit http://mail.live.com/mail/policies.aspx as well as this interesting discussion here http://community.office365.com/en-us/f/148/t/174524.aspx