I have a client with an unusual email requirement. They have a form on their site which captures a fairly low level of submissions per day - yet those submissions are extremely critical. They understandably do not want to accept anything less than a 100% deliverability rate of their transactional emails.

I have set up the best SMTP solution I can find which integrates the form with a third-party company offering good deliverability, but I am still (very) occasionally seeing forms that are sent, yet not delivered due to the vagaries of the email system (the last one was not being able to find the MX record of our domain, because I assume the DNS server glitched).

What techniques can you suggest to improve deliverability?

  • 2
    Store the form in a database, that guarantees durability. Then separately, schedule a task to read the database and send the email. If anything fails, data is still in database and a new email can be attempted at any time. Jul 8, 2022 at 20:53
  • 1
    Who is this email getting sent to? Usually email from submissions to the website gets sent internally, for example when a contact form is submitted. Is that what is happening here, or is the mail getting sent externally for some reason? Jul 8, 2022 at 22:28
  • Related to @StephenOstermiller question - who is the mail service provider which hosts the recipients email and whose nameservers are used for the domain? A robust system should not have DNS server glitches - DNS is distributed.
    – davidgo
    Jul 15, 2022 at 5:26

3 Answers 3


What techniques can you suggest to improve deliverability?

Change paradigm. E-mail can fail for so many reasons. Deliverability cannot be guaranteed. Tracking is missing.

An idea: save the form submissions to a database, build a dashboard for your client so they can review those form submissions. It has to be reasonably convenient, eg with some filters, show new messages and the ability to acknowledge unread messages etc.

But wait, it's actually called a CRM (Customer relationship management). There are some benefits too, in terms of customer follow-up and nurturing business. It does more than just collect leads.

So you could build some simple stuff, or instead capitalize on software that already exists (even open-source-. While that exceeds your client's immediate requirement, it would more effectively address the issue at hand.

In case they are already using an ERP, then it's a matter of finding the right plugin and deploying it.

  • This is I believe the answer, but my next problem would be storing the emails which are of a sensitive privacy nature! Thanks very much for your input. Jul 16, 2022 at 8:32

I'm not sure any company guarantees 100% deliverability. Even Google with all their expertise re. email offer only 99.5% SLA for mail (https://workspace.google.com/terms/partner_sla.html).

Can the form be delivered direct to the company's email server, without going through third-party SMTP solutions? It it feasible to use commercial-grade DNS to prevent rare DNS failures? If so, the deliverability should be the same as for the company's internal email, which should be acceptable IMO.

Otherwise, one of commercial-grade CRM's could be a way forward as kate mentioned earlier.

  • 2
    Ironically, using a specialized third-party provider will quite probably improve deliverability due to superior IP reputation. But even if the mail was delivered straight to the mail server and acknowledged, there is still the possibility of local antivirus/antispam software wrongly discarding the mail after it has been received. Not to mention what the mail client software could do. Ensuring end to end delivery of the mail is not the end of the story.
    – Kate
    Jul 14, 2022 at 20:11

To improve your deliverability, there are several things to check if they are correctly configured:

  • DKIM
  • SPF
  • MX PTR

Once those are set, you need to:

  • Monitor your IPs blacklists reputation
  • Configure unsubscribe headers for your mailing lists
  • Continually prune your subscribers' list (removing hard bouncers)
  • Throttle the number of mails sent to the same provider

Before you send a message to your list, you can verify it through an external email checking tool to see if other flags appear (spam words, HTML ratio, etc.).

Last but not least, you should use Google's and Microsoft's postmasters tools to monitor all things relating to sending emails their way:

Completing all these steps doesn't guarantee 100% deliverability, but will greatly improve your sending rate from reaching your audience.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.