Email Delivery Log message: Unable to connect to MX servers: []?
Using Jamroom
icw- see this related thread where I have recently been having a lot of these similar email fails:
https://www.jamroom.net/the-jamroom-network/forum/my_posts/35425/some-aol-addresses-clogging-email-delivery-failures
Are your and my issues in fact the same? (see my screenshot in that thread )
I contacted Mailgun and this is what they told me:
"The error that you are seeing is ESP throttling, and this occurs whenever the recipient's email service provider (ESP) has received a large number of emails from a specific IP in a short amount of time. Due to this, they will not accept messages for a certain period of time (usually an hour) until they have processed all the emails from the original batch sent.
The error code of "421" indicates that this is a soft, temporary bounce. Whenever we attempt to deliver a message and the recipient server returns a soft bounce, we will retry delivery for up to 8 hours in the following intervals: 10 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hour and 4 hours. Unfortunately this cannot be adjusted and is hard coded in our environment.
I have gone ahead and moved you to a less busy IP, this should reduce the throttling."
That was 2 days ago, and it's happening less now, but still happening- especially with certain AOL member addresses. I'm not so worried about it right now, because I suspect AOL will fix this when their customers complain more, and also I was assured it would not effect my mailgun 'reputation'. FWIW, most of those failed messages do seem to eventually get delivered after two or 3 failed attempts.
