If you’re seeing a lot of messages about untrusted TLS connections in your mail log when running postfix like this…
Untrusted TLS connection established to ASPMX.L.GOOGLE.com[220.127.116.11]:25: TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
… there’s a pretty easy fix.
We all agree that email is crucial to modern life.
But what email should you use?
Everyone gets email when they sign up for high speed internet service … the problem is that you’re tied to that internet service for that email address. If you switch service providers, you could lose the address. Even worse, if your provider goes out of business, you could loose access entirely. Sometimes the email provider charges a fee for better service and/or removing advertising.
Yes, you could use Gmail, Hotmail, Yahoo, or AOL, but you’re still tired to the provider. Plus, you don’t often get to choose the best address (firstname.lastname@example.org just isn’t that sexy).
Wouldn’t it be nice if you could get an email address that belongs to you forever?
This post is as much to help me remember as it is to help other people.
Below is a list (not comprehensive) of the postmaster resource pages for some of the major email providers.
On these sites you can get information about how the provider handles spam, feedback loops, blacklists, whitelists, etc.
Very useful for those managing mailing list servers.
Spammers quite often ‘spoof’, or fake, the from address of an email.
As a result of this, many unsuspecting domain owners are being ‘blamed’ for spam that appears to come from their domain.
Fortunately, there is a relatively easy way to protect your domain from this: Publish DMARC policies.
If you are publishing SPF records and signing your email with DKIM, you can publish DMARC policies that tell receiving mail servers what do with emails that don’t align with the SPF and DKIM information.
SPF policies are DNS records that indicate what mail servers your mail is sent from.
DKIM is a way to add digital signatures to your email so that receiving mail servers can verify it was sent from an authorized source and that it wasn’t modified in transit.
Now what if you have a domain that you NEVER send email from?
Protecting those domains from being used in spam is even easier.
Well, our good friends at Yahoo are at it again.
Once again they are deferring mail for no apparent reason.
Nothing has changed on my system and yet they haven’t accepted a message to deliver to one of their users in 3 days (maybe more). And, of course, there’s no way to actually contact a human to find out what is going wrong.
I’m on Yahoo’s email feedback loop … so I’m notified when someone complains about a message. Nothing has come in recently from the feedback loop.
I used to be on their bulk sender white-list. There was never a mention of having to renew the white-list approval.
A note to all my friends … DO NOT USE YAHOO FOR EMAIL! Especially for business email. The folks at Yahoo do NOT know how to provide service.
Gmail doesn’t have this problem … nor does Hotmail (much as I love to hate Microsoft).
Oh, and FWIW, yahoo customer service tends to ignore questions that are too complex for their script reading drones to answer.
A while ago I added a new anti-spam technique to my mail server setup called “No Listing”.
No listing basically means putting a high priority MX record in the DNS that always rejects mail server connections..
It seems, however, that the qmail mail server can’t cope with that. It’s not RFC compliant.
Here’s a tip for internet domain owners:
Make sure the contact information for your domain has more than one email address. And make sure at least one of those email addresses is not in the domain itself.
If your email starts malfunctioning, you want people to be able to tell you about the problem … and if the only email addresses you list are in the actual domain, they won’t be able to contact you.
For example … if the mail server for example.com is having problem … and all the domain registration in the whois database shows ‘email@example.com’, Joe won’t be able to be notified there is a problem.
The contact information is publicly accessible via the ‘whois’ databases.
Domain registrars that offer whois privacy capabilities should let you list more than one email address when they redirect the email address that they list in the whois look-ups.
For privacy sake, I like using a PO Box for the mailing address on all my domains.
Recently I’ve been getting a lot of mail from the feedback loops I subscribe to indicating that someone has gotten a subscription confirmation message and they considered it spam.
After digging into my logs I noticed a few things …
- The subscription requests are being initiated from TOR exit nodes.
- The web requests that initiate the subscription have “mailbait.info” as their referrer.
This ‘mailbait.info’ service is supposed to allow you to fill your mailbox … why anyone would want to do this is beyond me … and it has absolutely ZERO protections against submitting someone else’s email address. As such, it just ends up generating spam. And a lot of the twits that are using this ‘service’ are hiding behind TOR nodes, which protects their IP address.
And you probably read in my last post … I had a problem getting mail setup my new Android phone.
I could receive mail fine … but it failed (with a totally useless message) whenever I tried to send mail. I was sure I had the settings right (userid, password, ssl, etc).
I have my mail server configured to do authenticated sending (as all good mail server admin’s should) … but for some reason the authentication wasn’t working correctly.
I tried various setting combinations to see what might be the problem … I verified the settings with my iPhone and Thunderbird. Everything matched up.
I really wish there was a way to indicate, in DNS, that a domain never sends mail.
That way, if a mail server recieves mail claiming to be from that domain, it can be discarded out of hand.
I’ve got a bunch of domains that JUST do web serving … they never send mail. If the web server that they are hosted on does send mail, it’s sent from via the midrange.com mail server (and is identified as such).