Problem with Amazon SES Undetermined Bounce Status | Hacker News Reader

Problem with Amazon SES Undetermined Bounce Status

2 pointshackmyway2 comments

We are using AWS SES for sending emails. We send 10M+ emails per month using SES. For some users we received SQS bounce response status = 'undetermined', sub_status = 'undetermined'. We mark users with bounce status 'undetermined' as hard bounce and don't send them email in future. However we found these emails are valid. Emails should be delivered successfully. We observed this for multiple emails. Question: 1) Why 'undetermined' bounce response is received even for valid emails? 2) Should bounce response with 'undetermined' status be marked as hard bounce? Is the logic correct? SES bounce status & sub status details are in this link: http://docs.aws.amazon.com/ses/latest/DeveloperGuide/notification-contents.html

Have you looked at the domains that you are seeing undetermined status for, is there a pattern?

We send a reasonably decent amount of email, in general we distribute the emails across multiple ESPs, with a small amount going through SES. One of the easiest ways to figure this out is to trap the entire SMTP conversation and codes. We wrote an internal tool that will send an email and trap the entire SMTP conversation so we can see what is really happening, as not all ESP's correctly categorize things, nor do they let you see the raw SMTP conversation and many times incorrectly configured mail servers cause the problem (even on "big" domains).

In a couple of cases we have found that some domains work better when we send to them using a specific ESP, which is part of the reason we integrated to multiple ESP's. We also built into our system the ability to pin a domain to an ESP, thereby usually increasing our deliverability for clients.

EDIT: And no, I do not believe an undetermined bounce status should be a hard bounce, soft seems more reasonable.

I checked the domains of emails. There was no specific pattern or for specific domains it's happening.

Do you always mark undetermined bounce status as soft or is there any logic based on counters. e.g. for the same email 1st 3 undetermined responses are soft after that it's hardbounced.

Makes sense?

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