Help with email get stuck

[mikew]

Do you know what error codes you are getting ?

I have been having similar issues with 4.0.2 and have a post over here that I am sure someone will help out with shortly and this should fix your problem as well:

mautic.ERROR: [MAIL ERROR] Expected response code 250 but got an empty response

We are experiencing the same issue with Mautic 4.0.1 with Amazon SES. The weird thing is that some emails are going through. We are running a campaign with around 300,000 contacts, and I am seeing the log start to fill up and also noticing lots of failed events. In the system log I am getting messages like this: [2021-11-18 18:24:51] mautic.ERROR: [MAIL ERROR] Expected response code 250 but got an empty response (send); kfdsfd@wfdsf.com {"exception":"[object] (Swift_TransportException(code: …