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Willem
Asked: 2015-02-05 04:57:38 +0800 CST

Reliably send small amount of mail from possibly blacklisted cloud IPs

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So you boot a new cloud server. Only to discover that its IP is blacklisted by misbehavior of the previous owner. How to make sure your mail gets delivered for a modest price?

Context: I provide my customers each with their own cloud server. They use it to send on average 20 mails per day to their customers, using their own domain name. I have a couple of hundred customers/servers and I plan to have many more ;)

I have looked into Sendgrid, Mandril, Amazon SES, Mailjet, Mailgun but they are all focused on large marketing campaigns, not the occasional mail senders like my customers are. For example, with SendGrid I could create (by API) a "subuser" for each of my customers, but if my customer wants to get rid of the pesky "via sendgrid" header in Gmail/Outlook (and they want that), they are required to pay $20/month/domain. That seems quite expensive for sending < 100 mail. Plus it is a complicated procedure, which would be required for each of hundreds of domains.

So what I want is a basic SMTP relay service, that will somewhat reliably deliver my small volumes of mail for a modest price. It should support segmentation, ie if one customer somehow sends spam, he should be blocked but it shouldn't affect my other customers. Bonus points for not having my customers go through complicated domain verification procedures (ie. not DKIM).

How did you handle this issue?

TIA!

cloud

2 Answers

  1. If you don't want to use SES or the like (which is what I'd recommend, even for small volumes), then another alternative is to stand up your own mail relay outside the cloud provider, on a non-blacklisted IP and have your servers relay through that. I've had good luck with Linode - I've never landed on a blacklisted IP there.

    If you do this, make sure that you require authentication so that you're not an open relay.

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  2. So, I did extensive testing with all of the SMTP relay providers (ESPs) above.

    So to sum up the requirements:

    1. ESP has multi-tenant features, such as subaccounts and containing misbehaviour within a subaccount.
    2. My customer (end-user with own domain) shouldn't be bothered with manual domain or address verification procedures to enable the delivery of mail.
    3. My customer, if he desires so, should be able to eliminate the via tag from Gmail/Outlook for a modest amount.

    Strangely enough, only SendGrid and Mandrill will deliver without verification of the sender domain.

    Both support multitenancy (Although Mandrill has a strange quirk where each subaccount requires the master API key for SMTP authentication. There is a hackish workaround though.)

    Both enable the elimination of the via tag, however SendGrid will charge $20 per month per domain to do that. Mandrill will do it for free.

    All in all, Mandrill is quite cheaper. Given 100K mails,

    • Mandrill will charge $17.60
    • SendGrid will charge $79.95

    I have not tested the quality of delivery thoroughly yet, although some samples with Mandrill showed a delay of 1m30s for delivery to Gmail (for just a single mail). The latter indicates that Google is throttling Mandrill.

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