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emailmandrillemail-bounces

Dealing With Mandrill Soft Bounces

I use the Mandrill API to get the rejection list, and currently for entries where they are marked as hard-bounce, spam or unsub I remove them from my mailing list so that I will not attempt to send to them any more.

However, I am not sure how to approach dealing with addresses that have been marked as soft-bounce.

The documentation seems to indicate that these may be transient errors, and that unlike say MailChimp, soft bounces don't harden over time.

Mandrill doesn't automatically convert soft bounces to hard bounces. If you're seeing a lot of soft bounces to an address, it may be a sign that the address is unusable.1

How have others approached these soft bounces when trying to keep their lists high in quality? I have considered maybe keeping a count of how many days they have been there, but I have no way to know how Mandrill determine how long that they keep items on the list before attempting again.

In summary: How should soft bounces be managed by the sender to ensure high quality lists?

Here's an example of the JSON returned on one of my soft bounces that should (by looking at the obviously fake email address) be eventually removed:

{
  "reason": "soft-bounce",
  "detail": "smtp;550 \"aaa@wp.pl\": This account is disabled or not yet active (#5.1.1)",
  "last_event_at": "2015-10-06 10:16:46",
  "email": "aaa@wp.pl",
  "created_at": "2015-10-02 10:10:56",
  "expires_at": "2015-10-08 10:16:46",
  "expired": false,
  "subaccount": "XXXXXXXX"
  ,"sender": null
}
Solution

  • In a previous job position I worked with +40K email contacts in Mandrill. What we did was the following:

    1. Send out emails
    2. Hard bounces were deleted from the Mandrill system every 12 hours
    3. Soft bounces were moved into a 'grey' list that we used to sent another email 3 days later
    4. If after 3 days email was sent, 'good' email address was sent back to original list
    5. If after 3 days we received another soft bounce, the email was purged as well from the 'grey' list
    6. Repeat step 2

    This way we kept the list healthy.

    Note: The soft bounces are not handled anymore by Mandrill, as this depends on the receiving mailserver how many tries the email gets.