Mandrill Emails not reaching any mailbox, but Mandrill showing status 'Delivered'

Question

Mandrill does not offer any support. I've sent them many tickets, but still no answer. I hope someone here will help me out.

I'm sending emails through SMTP. I'm able to send few thousand emails in start, but after few thousands, no email reaching any mailbox. Mandrill activity showing that the email is delivered, but it's not and there's no email in backlog. I have limits around 50K/hour.

I tried making another account after a day, and did some deposit too, but same thing happen with other account too. No error in SMTP client, no error in logs, nothing.

Other thing to notice is, when I hover over 'Delivered' it says "No SMTP event", but emails which are actually got delivered, showing some stats on hover over.

Solution 1

The Mandrill Delivered-status in the UI doesn't actually mean that it is sent, only that Mandrill have received the message for processing. This is of course extremely confusing.

The only way of seeing if an email is actually sent (i.e. successfully delivered to the receiving mail server) is to see if the message has smtp-events. Do note that it can take some time before the SMTP-events are available in the GUI/API (I have experienced a delay of between 2 minutes and 24 hours).

To see all emails that not currently confirmed delivered you can search for "NOT smtp_events.diag:250" in the search field.

Solution 2

It turns out to have been a delay in the emails being received by the mailserver (gmail). It appears as if they were accepted and not processed for a few hours.

Solution 3

After some research, one of the reason, I came to know that if TEST API KEY gets used to send emails, no mail is actually sent to inbox, but webhooks trigger normally and it shows status as delivered on the Mandrill UI. In order to check actual delivery of email to your inbox, please try to use different API KEY other than test account

Solution 4

I had run in to the same issue and this explanation given by OakHosting_James helped me a lot in understanding what is going on:

It turns out the message was sent from IP that is on an RBL (it happens - I get that). So the receiving server rejected the message at SMTP time.

They replied to say two things about that:

(i) Anyone can set up a blacklist and put any IP on for no good reason. (ii) Some messages bounce in such a way that Mandrill is not able to detect that it's bounced - which is why their website said "delivered".

Let's take those issues:

(i) It's true, but this was UCEPROTECT-Level 1. They're not a pleasant blacklist to work with, but they're not a backyard project for someone with an axe to grind. I still get the fact that it's impossible for any sending network to remain 100% clean. I'm not frustrated that one of their IPs was listed temporarily. But I did feel fobbed off by being told that there are some tiny blacklists out there that no-one in their right mind would use. UCEPROTECT is not one of those, and they should have come clean: "Even with the best spam protection, we get blacklisted occasionally; we detect this very quickly and switch to other IPs."

(ii) I'm sure there are some after-the-fact bounces that Mandrill's system can miss. But this was rejected at SMTP time. How can they mark a message that never left their sending server as "delivered"?

So the solution (to some degree) to the RBL IP problem (i) could be an "Dedicated IP $29.95 / month" for your account in Mandrill. But using a dedicated IP can be a problem on it's own and is for most cases not advised.

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