Emails very delayed getting from mandrill to gmail

I had similar issues with delays on emails sent via Mandrill to gmail.

To fix the issue I viewed the "Sending Domains" page under "Settings" in Mandrill. I discovered the DKIM and SPF DNS records were either missing or not valid. Mandrill will provide you with new values by clicking on the "View... settings" link. After updating these settings we no longer experience the delay.

I've run into this issue a number of times. Our DNS settings were all good (DKIM and SPF confirmed my Mandrill) and after some investigation (looking at the headers of the delayed emails) the delay appeared to be entirely on Mandrill's side (once it was handed off to Gmail or Yahoo the delivery occurred within a second). When I contact Mandrill support they explained why we were seeing these delays:

In looking over the logs for your account we are seeing intermittent delays for some of your recipients. Generally, the speed of delivery in most cases depends largely on the receiving domain, and how quickly they will receive and process emails. Most of the major email providers limit how much email they'll receive in a certain period of time, and will restrict delivery—Mandrill's sending servers are designed to queue and back off sending if this occurs. In these cases, the receiving mail server or ISP will return a specific kind of SMTP response telling Mandrill's servers to 'back off' and 'try again later,' which ultimately results in the message lingering on our mail servers longer than expected (and since the message isn't passed off to the receiving server at that point, and we're only getting a 'try again' response, you won't see that information in the message headers of the final email you receive. You'll only see that the email stayed on our servers for a longer time period which can be confusing).

Additionally, even though we may hand the messages off to ISPs for delivery almost immediately, it's still up to that ISP, like Gmail or Yahoo, to actually to process that email and place it in the inbox. Each receiving server is different though, so it may take a different amount of time for Yahoo to process the mail than Gmail, for example. In many cases, things like the time of day and overall email traffic to that recipient server can affect how quickly they're able to receive and process email.

All that said, the delays you're seeing generally aren't expected, and while we see that messages are ultimately delivering, we are detecting factors on our end where we may need to make some changes to help mitigate further delays. Our delivery team is continuing to monitor traffic to major ISPs and will make necessary adjustments as needed.

We still periodically see these delays, though they've improved is so the delays are rarely longer than 10 minutes or so, but it still can cause issues with things like password resets or confirmations that are time-sensitive. Bottom line: Mandrill is awesome for bulk mailing, but if you need instantaneous delivery you may want to rely on a different or self-hosted service.

In mandrillapp.com > Settings > Domains > Sending domains, verify these 3 points:

• DKIM is valid,
• SPF is valid,
• domain is verified.

I also had gmail showing emails sent through mandrill around 10 minutes later. And that is unacceptable to register confirmations and password resets.

I had configured my DKIM and SPF dns records and mandrill reported all green in this records.

But mail delivery to gmail was always delayed with no aparent reason.

After a while I decided do test/use my own email server to do this, instead of mandrill. Now there are no delays in gmail. I'm happy :)

After this I think I will only use mandrill for massive email delivery / marketing, where delays are not important. Time will tell.

Would like to hear other people about this subject.