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0 pointsdjsumdog9y ago0 comments

Yep, I wrote one not too long ago:

http://penguindreams.org/blog/how-google-and-microsoft-made-...

I've been meaning to write a follow up after I met some MailChip devs at a conference. They told me at MailChip they have to slowly spin up new servers, sending e-mail through them slowly so Google registers their new SMTP IPs.

The other thing they told me: MailChip owns a /A, and can therefore separately out their servers from even being remotely related to any spammy subnets (common problem on 'cloud' hosting).

I'm wondering if I heard/remember that correctly. I mean, a class A is huge and would be crazy expensive. I've been looking through websites on ASNs and am trying to figure out how to verify that info.

0 comments

drv9y ago

(Assuming you mean MailChimp)

I don't know anything about how MailChimp operates, but a quick search turns up this blog post about how to set up SPF records [1].

From there, you can get a list of which IPs MailChimp authorizes as a sender; following the SPF include directive, you can see they specify two IPv4 ranges, both of which are in class C space, so it seems unlikely that MailChimp has their own class A for SMTP senders.

[1]: https://blog.mailchimp.com/senderid-authentication-for-your-...

dunham9y ago

Yeah, we do something similar, although we send a much smaller amount of email than MailChimp.

Our admin runs about 10% of the outgoing mail through our DR site to keep google et al trained to accept emails from those IPs.

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