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?