One of my customers (annoyingly) uses Hotmail for his primary email address. A lot of the time, my emails to him get returned undeliverable due to an over-zealous spam filter.

My email is from my own company domain, signed with a valid certificate and the domain supports Sender-ID and SPF. My belief is that the provider of my domain's email hosting is using the same SMTP server for multiple customers, some of which are abusing it and hence getting the server blacklisted by Hotmail.

Is there anything more I can do with this setup?

Or am I going to have to head over to Server Fault to find a provider of dedicated email servers (don't want full web hosting and all that crap, just POP3/IMAP and SMTP that works)?

  • 3
    Not convinced this should have been moved to Web Apps, since I was sending to a Hotmail user not *from Hotmail, but whatever....
    – Rob Cowell
    Jan 21 '11 at 9:05

The only thing I can think of that doesn't involve changing hosting is to get your customers to add your e-mail address to their white list.

I know it's not ideal, but I see it on a lot of mailing list mails for this very reason.

  • 1
    I guess that solves it for one customer - if I don't get a better generic solution (i.e. a fix for all hotmail recipients), I'll mark yours as the accepted answer
    – Rob Cowell
    Sep 11 '09 at 9:39

Even with SenderID and DKIM both properly configured and tested, we can't get our Stack Overflow mails through to hotmail.com email addresses -- they regularly go in the spam folder.

Apparently hotmail is a tough nut to crack...

The autoresponder at check-auth@verifier.port25.com is a great resource for this. Send an email to it with a valid reply address, and it'll tell you what isn't configured properly.

  • As for "they regularly go in the spam folder": any idea if similar messages go into the spam folder for some users, but not for others? Or do you think that it is the body that yields the spam score (as the headers are probably fine)?
    – Arjan
    Jan 8 '10 at 17:57
  • Hmm. I will have to test that, but the content is quite innocuous and isn't flagged for spam via the check-auth@verifier.port25.com either .. (it does a spam/ham test as well) Jan 8 '10 at 19:22
  • Could it be that too many Hotmail users have hit the "Mark this as spam" (or equivalent, I'm not a hotmail user so don't know the exact wording) because they're too lazy to correct their email preferences?
    – Rob Cowell
    Jan 10 '10 at 12:24

Microsoft relies on various authentication filters to determine if an email is spam or not.

Common industry practices include reviewing email for the presence of a SPF Validation, Sender ID and DKIM records within email received.

The Sender ID Framework is an e-mail authentication technology protocol that helps address the problem of spoofing and phishing by verifying the domain name from which e-mail messages are sent.

SPF (sender policy framework) is essentially an extra DNS record that directly specifies where remote mail servers should be expecting to receive mail from.

DKIM (DomainKey Identified Mail) is a newer implementation of the older DomainKeys system, which is essentially a more complex approach toSPF/mail verification, that requires mail to be signed with a private key, and checked against a public key found in the DNS record. This essentially acts as a more secure version of SPF.

You can send an email from a test@domain.com to check-auth@verifier.port25.com when sent, an email will return stating the verification of DKIM, DomainKeys, SPF, SpamAssassin, and Sender-ID.

However, in recent months, I have found that despite including these elements with emails sent out, Microsoft was still ditching legitimate emails. I found that once the recipient had our email address listed as a saved contact, they received our emails fine. So I’ve created a vCard for our company and urged our customers using Hotmail or Windows Live email services to save the vCard as a contact to ensure that our emails get delivered correctly.

  • 1
    From all the proposed solutions you stated, getting added as a contact by the recipient (or being added to the whitelist in Hotmail) was the only reliable way to get the mails delivered.
    – Bob
    Aug 18 '15 at 19:52

You might have a look at MSN's Sender Solutions which describes (quote)

a suite of services to help senders improve their deliverability to Windows Live Hotmail consumers

  • 2
    Have emailed postmaster, have set up SPF and Sender-ID. I draw the line at being accredited by a third party (Sender Score Certified Email) as I don't believe I should have to pay out extra money just to be email to send emails. I've jumped through enough hoops getting signing and SPF/SenderID set up already.
    – Rob Cowell
    Sep 11 '09 at 9:30

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