Emails from Cloud Server – Part I

Practically Speaking About Cloud Computing:


Recently we had a practical experience of migrating one public website to cloud hosting. The site was with a leading hosting service provider and migrated to a leading cloud service provider. One of the issues that we faced and sorted out is sending email from cloud. Of course for those who are involved in cloud migration of websites, this should be a known issue by now. When we host sites in the physical server, we configure mail servers for sending emails. There is default SMTP (Simple Mail Transfer Protocol) server. As they are configured with static ip address, the emails sent may not end up as SPAM mail. However when we do the same from cloud hosting, there is chance the mails end up as SPAM and rejected undelivered. This is because the ip address pool is in the blacklist.

Real Time Blacklists:

Real Time Blacklists (RTB or RBL) are collection of mail server ip addresses that are decided as SPAM mail senders by the list managers. Also, called as DNSBL – DNS Based Blacklist.  When an email is sent from a smtp server covered by the blacklist database, they are rejected un delivered. Most of the cloud hosting provider’s ip address pool is listed in these RTB/RBL/DNSBL databases. So sending mail from cloud ends up as SPAM and undelivered. While cloud is considered great for hosting, for sending mail whether cloud is great or not, the question arises. Cloud service providers like Amazon Web Service, Rackspace are aware of this issue and they too are concerned. However they are not in a position to deal with multitude of these blacklist maintainers as there is a large sum that is demanded as donation to remove block of ip addresses. There are some solutions to practically sort out this issue. One option is availing the service of third party smtp service providers.

Third Party Email/SMTP Service Providers:

Basically, availing the services of email service, can be for transactional requirement (like sending an acknowledgment mail automatically for registering in a website) or for bulk email dispatch (like sending newsletters or marketing campaign mailers). We resorted to the solution of going for a third party smtp service provider with additional cost (in addition to cloud hosting cost). There are many Email Service Providers to cater to this need; each having different pricing plans.

Just to list a few of them known to us:

  • AuthSMTP
  • JangoMail
  • SendGrid
  • CloudSMTP
  • CloudRelay
  • Postmarkapp
  • Mailgun
  • Mailchimp
  • Elasticemail

Going in for one of these ESPs solved the problem of sending emails; though this added to the cost. Let us discuss this further in Part II.

By Malick of CloudTweaks

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