Email blocklists
Email blocklist monitoring
Your sending IP and domain against fifty blocklists.
What it is for
Being listed is the failure with no error message. Your server is healthy, your queue is empty, and a portion of your mail is being dropped silently by receivers who will never tell you. Most people find out when a customer mentions, weeks later, that they never got the invoice.
We check the IP and the domain against fifty lists every hour and tell you which list, so you can go and file the delisting rather than work out where to start.
Like every check here, it runs from Amsterdam, New York, Sydney and Singapore, and a failure is confirmed from two other continents before anybody is woken. How that works.
What you can set
Everything below is on the form when you add one, on every plan.
- What to check
- A sending IP address or a domain. Both are worth watching: they are listed separately and for different reasons.
On Starter, Pro and Business, checked hourly, and the interval is not adjustable. One check is fifty DNS lookups, and a product that let people run that every minute would be delisted as an abuser, which would make the feature worthless for everybody using it properly.
Questions
What is a DNSBL, and is an RBL the same thing?
The same thing under two names. A blocklist publishes itself as a DNS zone, so asking whether an address is listed is a DNS query for that address reversed under the list's domain. An answer means listed and the answer's value says why. RBL is the older name and you will see both, along with blacklist, which is what most people still type.
Do you check Spamhaus?
No, and we would rather tell you why than leave you guessing. Spamhaus will not answer questions from servers like ours, and when they refuse, the answer looks exactly the same as "not listed". We will not show you a clean result we never really got, so we leave Spamhaus out instead of including it and being quietly wrong.
Which lists do you check, then?
Over fifty for the sending IP, Barracuda and the other lists a real mail operator would act on, and SURBL for the domain, which is a different problem: your domain can be listed because of somebody else's botnet while your own IP is spotless.
My IP is clean and my mail still lands in the spam folder. Would this have told me?
Only if a listing was the cause, and often it is not. Deliverability also rests on SPF, DKIM and DMARC lining up, on what the message says, and on the reputation the receiver has built for you privately, none of which a blocklist lookup can see. This catches the listing, which is the cause with no error message attached.
Do you check my PTR and reverse DNS?
Not in this check. A sending IP with no reverse DNS, or with a generic one from your hosting provider, is a real reason for mail to be refused, and it is a record rather than a listing. A DNS monitor on the PTR record, with the name you expect, watches it properly.
How do I get delisted?
Through the list's own form, which is why the alert names the list and the code it answered with rather than saying you are listed somewhere. The check runs hourly, so you hear about it within the hour and you can watch it clear without having to ask anybody.
Why not just look my IP up on a blocklist site when mail bounces?
Because by the time mail bounces, the damage is already a week of invoices and password resets that never arrived. A lookup site answers the question perfectly; the problem is that nobody thinks to ask it until something has gone wrong. This asks hourly, across fifty lists, and tells you on the day a listing appears, which is when getting delisted is easy.