Does volume cause blocking?


There seems to be a never ending debate about volume and how it affects delivery and revenue. I regularly get questions asking if ISPs block senders just for volume.
The answer is no. Unless you’re actually sending enough mail to overwhelm the incoming infrastructure, something that’s difficult on today’s internet, you’re unlikely to be blocked due to simply sending a high volume of mail.
Sending mail recipients don’t want, or mail that looks like spam, that will get the mail blocked or filtered.

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  • The spam problem is caused by volume. If there were only single, personally typed spam messages we wouldn’t need to spend all this effort filtering.
    I have had multiple instances where Cisco Ironport has blocked mail from a domain, or from an IP range because there is purportedly spam coming from there.
    While I can understand that, the problem I had was that a single, personally typed message from me was not getting through to my city councilman. The city that I live in.
    I pointed out to Cisco support that you cannot solve a spam problem by blocking one personally type message.
    And I pointed out to the city manager that if you use Cisco Ironport and it blocks single, personally typed messages from constituents, well, I suggested to the city council that perhaps Cisco Ironport was only suitable for use on a hobby email account. It was too egregious for business or government use. They shouldn’t use that.

  • True, but “the spam problem is caused by volume”, as the previous commenter says, is also true.
    I’d say that the less clean your (outbound) mail stream is, the more volume will hurt your delivery rates. You could solve that by sending less email, but it’d be a lot better – both for your business and for the Internet as a whole – if you just cleaned your mail stream.

  • Another case scenario – One of the bigger insurance guys started ramping up mail volume on their new IP’s over few days and had to be throttled. Improper warming up might result in volume based blocks as new IP’s would be treated with suspect. And still see lots of these cases.

  • As Laura said that most of the major ISP’s don’t block mail just based on volume only. ESP’s always has this concern that why my mail is getting blocked when I sent higher volume? Well, most of the time with higher volume, most likely users on the ISP side are complaining about that mail and filters kicks in and give a volume threshold blocks but in actually there are other lingering issues with IP/domain/content. Say for example if American Express sending statements from a single IP with higher volume will not get blocked compared to that same American Express sending marketing mail from a different IP will get rate limited due to the factors explained before.

  • @Laura – I have seen AOL repeatedly volume threshold block clients sending 2-3x more mail than they typically send in a given day, returning the Technical Bounce ESMTP “not accepting connections”. If they spread out these messages or throttle them, we dont see any issues, and I would imaging if the block is due to complaints or something else, AOL would return a CON:B1 error or something other than the ESMTP. Personally, I feel certain ISPs (mainly AOL) are very sensitive to jumps in volume and would disagree that a spike in volume itself, isn’t the reason for a block. Thoughts?

  • Anthony: A significant increase in volume can cause throttling at some ISPs. But it’s the change that’s the issue – the filters don’t know what has happened and so they throttle until they can figure out if the mail is good and wanted or if it’s spam. Once the filters adjust to the new volume, then there shouldn’t be filtering, as long as the mail meets the ISP engagement / complaint / bounce standards.
    It’s the same with warmup. The raw volume isn’t the issue, it’s the change in volume. Filters recognize what a normal volume from an IP is, and expect that volume. Warmup is just controlling the volume so the filters can adjust. You don’t have to warmup an IP, you can just send and the filters will adjust, but there’s probably going to be huge queues in the meantime.

  • Hi!
    While ago I got message from Microsoft due limits:
    Reputation has been ok, but magnitude has increased up ~150% due previous month average per day! It has been the reason why Microsoft denied to delete that IP!

  • A significant, quick increase in volume causes blocking or filtering or throttling, yes.
    When somebody gets blocked, you or I look to what changed. What changed? Volume changed.
    Thus, volume does causing blocking. The answer is yes, from where I sit.

  • Once the higher volume is established as normal and wanted there is no blocking or throttling. So it’s not the volume causing the blocking, it’s the change.

By laura

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