Our spam filters appear to be blocking some mail being sent from gmail, Yahoo Mail, Outlook.com, etc. The error message sent back to the sender usually says something like this:
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain (yourdomain) by mx11.spamquarantine.com. [126.96.36.199].
The error that the other server returned was:
554 Service unavailable; Client host [mail-pa0-f47.google.com] blocked using Barracuda Reputation; http://www.barracudanetworks.com/reputation/?r=1&ip=124.240.221.xxx
Why this is happening:
Gmail, Yahoo, Outlook.com, etc. offer free email accounts to the public. This is a magnet for spammers. They sign up for free accounts or they hack into existing ones and then use those accounts to send spam.
When this happens the sending mail servers usually get blacklisted. This is because the specific mail server at Google, Yahoo, etc. is sending out so much spam that it gets noticed by one of the major internet blacklisting services and ends up on their published list of bad senders. Lots of companies check these blacklists (including us) and restrict mail accordingly.
You have done nothing to cause this, and neither has the person who sent the message (usually). The sender simply had the unfortunate luck to have that particular message routed through a mail server that has been blacklisted.
Not all mail from Gmail, Yahoo, etc. is getting blocked, only mail passing through servers that are blacklisted. Google, Yahoo, etc. use hundreds of mail servers, and at any given time the vast majority are clean. When you send mail from Gmail/Yahoo/etc. you don't usually use the same outgoing mail server for every message. Your message could be routed through one of many many mail servers.
That said, there are two options to consider if you are experiencing this issue:
- Do nothing. This is our recommended approach. Keep in mind, our spam filters are doing exactly what they are supposed to - blocking mail from bad sources. These IP addresses are being blacklisted for a reason - they're sending out tons of spam.
It has been our experience that these issues resolve themselves quickly. The folks at Google/Yahoo/etc. usually find the problem in a timely manner and work with the blacklisting organizations to have their IP addresses removed as soon as possible.
- Whitelist the sending IP address in your spam account. If you absolutely need all email from the blacklisted IP address to pass through the spam filter, you can go into your account (if you have admin privileges) and whitelist the specific sending IP address (please let us know if you need help doing this). Be advised though that this should be a temporary measure because the problem usually fixes itself, and by doing this you would be allowing all mail from this IP address to pass through the spam filter. Basically you would be allowing all mail from a known spam source to pass through the spam filter and into your inbox. We do not advise doing this.
Simply whitelisting the sender's domain name or email address would not work in this case because the IP reputation check takes precedence over domain-level or account-level whitelisting. The whitelisting would have to be done by IP address.
Note: Keep in mind you are doing nothing wrong. You shouldn't have to change your policies and put your mail server at risk just to accommodate a system that allows spammers. This isn't really your problem, it's the mail provider's problem. They should work to fix it, and you shouldn't have to accommodate them.
Note to Senders Getting Blocked: This issue is not technically your fault (usually). You're just using a service where this is bound to happen. Free email services are a magnet for spammers and if you share a service with millions of other users, bad things can and do happen. A long-term solution to this problem would be to get your own domain and host your email with a reputable provider (contact us - we can help you). This option is not free but it is much more reliable.