Limit incoming emails from the same domain

Question

There are SPAM source verification policies that are based on the amount of emails that a given domain is sending per hour.

Such policies may be internal, such as those applied by Google, or general, such as SPAM lists.

When we talk about optimizing the sending of newsletters from an own solution the first concerns are not to lower the reputation of the sending IP or keep the same IP present in the most common SPAM lists.

In analyzing this, a question arose:

Nowadays, what is the limit that companies like the Google, Microsoft, Yahoo and others apply to discern whether sending is a trusted newsletter or a source of SPAM?

Of course, there are hundreds of methods in use to ascertain what is SPAM and what is not, but what you want to address in this topic is the limit of emails per minute, time or day, which we cannot exceed in such a way as to ensure that for example Google will not consider a particular address as a source of SPAM when it is only sending trusted newsletters!

Then comes the need to know:

┌─────────────────┬─────────────────────┬───────────────┬──────────────┐
│  Controlado em  │  Tipo               │  Limite por?  │  Limite de?  │
├─────────────────┼─────────────────────┼───────────────┼──────────────┤
│  Google         |  Provedor de Email  │  Hora         │  100         │
├─────────────────┼─────────────────────┼───────────────┼──────────────┤
|  Microsoft      |  Provedor de Email  │  Dia          │  100000      │
├─────────────────┼─────────────────────┼───────────────┼──────────────┤
|  Spamhaus       │  Lista de SPAM      │  Dia          │  1000000000  │
└─────────────────┴─────────────────────┴───────────────┴──────────────┘

Following trying to get these values or a reference line to plan the application efficiently came this information:

Google Apps - Receiving Limits ^(English)

...
If an Account Reaches the limit, a user cannot receive any new email ...

┌─────────────┬──────────┐
│ Per minute  │  180     │
├─────────────┼──────────┤
│ Per hour    │  3600    │ 
├─────────────┼──────────┤
│ Per day     │  86,400  │ 
└─────────────┴──────────┘

But this limit is for Apps accounts, and for Gmail? What about the others? A storm is being lifted in a glass of water?

Answer 1

The above limits are for google apps, but probably also apply to gmail.

However, these are limits of receipt and on behalf, that do not interest you, unless you intend to completely fill the user’s Inbox with your newsletter, which for me is spam.

What would interest you are IP sending limits, how many similar emails to different accounts gmail would accept before marking your IP as spammer.

This information is not published and in fact gmail (and no self-respecting ESP) should not use such a technique because all a spammer would have to do to avoid the filter would limit the number of spam sent to a certain domain per day.

What you need to do to ensure that your email is not considered spam is to take care of your IP’s reputation, which is a complicated process... Some tips to put you in the right direction:

• Make sure that your IP and other Ips in the neighborhood were not previously used by spammers. Getting already with bad reputation is horrible. Check the list sites, such as spamhaus and sorbs. Use mxtoolbox to see if your IP is not currently listed, and do so periodically. Ah, obviously your IP address should be fixed.

• Make sure your newsletters include a 'one click unsubscribe' link. And that users who click on it do not need to log in to remove themselves from their list and will no longer receive their newsletters.

• Use a double sign-up process (double opt-in), registration is only confirmed when the user clicks the link in the confirmation email.

• Make sure your MTA hostname has an A record and that the reverse resolution is valid. Hostname -> A -> Hostname

• Make sure your MTA cannot be used as an 'open Relay''.

• Use Mxtoolbox tools to see if there are other things to fix in your DNS.

• Ask your users to add it to the address list.

When these things are working properly, investigate:

• DKIM
• SPF
• Feedback Loops
• List-Unsubscribe header

The most important thing is to make sure that whoever is receiving your newsletter wants to receive it, can remove yourself from the list when you want and that your content is relevant.

Answer 2

I think that assuming that google offers a free email to the end user, as well as Hotmail, there is no way to reach the mailboxes of these users, in these services, efficiently, without a financial agreement, starting from a single IP. My tip would be that in case of mail marketing, you set up a large range of MX, and preferably in multiple domains. Thank you for the metrics already obtained and made available!