Email from MAILER-DAEMON@amazonses.com: Delivery Status Notification (Failure)

Question

i run a LAMP server on Lightsail to host a website for a small flying club. The website allows members to generate an email to all of the other members in the club (about 72 on the roster).

Users can log into the website and complete a webform, and PHP generates the email from the web form and sends it from amazonses.com with the reply-to address of the sender.
 
```
From: "[Sender name] via HarfordFlyingClub.com  via amazonses.com
Reply to: [sender email address] 
```

This has been working perfectly, but for the last couple of weeks I have been receiving an email with a list of emails that are un-deliverable, but with no good explanation. In the interim, I have been forwarding the email to the people on the list (22 people) from my gmail account and they send without issue - so there's no question that the receiving email accounts are active and able to receive email. Note that i only see gmail.com accounts in the list, but it's not nearly the full list of gmail accounts on the roster. I think that all of the rejected emails being gmail accounts is just coincidence.

Here's what the body of the un-deliverable notification email looks like:

```
MAILER-DAEMON@amazonses.com
8:07 AM (24 minutes ago)
to webmaster

An error occurred while trying to deliver the mail to the following recipients:
[list of 22-23 email accounts]

---------- Forwarded message ----------
From: "[Sender Name] via HarfordFlyingClub.com" 
To: undisclosed-recipients:;
Cc: 
Bcc: 
Date: Sun, 3 Nov 2024 23:07:00 +0000
Subject: Hangar Clean-Out
```

I had a similar issue a few years ago when the club reached over 50 recipients. I altered my code to break the email down to fewer than 40 recipients per email and send it in two separate emails. Has that number changed? E.g. can I only have 30 (or whatever) recipients per sent email now?

I did increase my send quota to 100 recipients per second (from 14 originally) a couple of days ago, thinking that maybe it was just sending the emails too quickly, but that didn't seem to fix the issue either as I just received another notification this morning.

It's frustrating that the error message has NO explanation about what's going on. I didn't see anything in my Apache logs, so I'm somewhat sure this is an Amazon SES issue.

Any ideas/suggestions?

re:Post Agent · Answer

The issue you're experiencing is likely related to email deliverability and reputation management within Amazon SES (Simple Email Service). While the exact cause isn't explicitly stated in the error message, there are several factors to consider:

1. IP Reputation: You might be using a shared IP address with Amazon SES, which could be listed on a spam denylist. This can happen even if your emails are legitimate, as other users sharing the same IP might have affected its reputation.

2. Sending Limits: While you've increased your send quota to 100 recipients per second, there might still be other limits in place. Amazon SES has daily sending quotas and rate limits that, if exceeded, can cause delivery failures.

3. Content Filtering: Amazon SES uses content filtering to scan messages for spam and viruses. If your emails are triggering these filters, it could lead to delivery failures.

4. Recipient Email Provider Policies: Since you mentioned that the undeliverable emails are mostly Gmail accounts, it's possible that Gmail's spam detection algorithms are flagging these emails for some reason.

5. Authentication: Ensure that your domain is properly authenticated with SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to improve deliverability.

To address these issues:

1. Consider using a dedicated IP address with Amazon SES if email deliverability is crucial for your club's communication.

2. Review your email content and sending practices to ensure they align with best practices for avoiding spam filters.

3. Monitor your bounce and complaint rates closely. Amazon SES provides notifications for these, which can help you identify and resolve issues quickly.

4. If the issue persists, you may need to contact Amazon SES support for more detailed information about why these specific emails are being rejected.

5. As a temporary workaround, you could try further reducing the number of recipients per email, perhaps to 20 or 25, to see if that improves deliverability.

Remember, maintaining a good sender reputation is crucial for successful email delivery with Amazon SES. Consistently high bounce rates or complaints can negatively impact your account's standing and lead to reduced sending capabilities.  
**Sources**  
[amazon simple email service spamrl.com error | AWS re:Post](https://repost.aws/questions/QUOuqYcByMRPS9JrYT8tH7Ug/amazon-simple-email-service-spamrl-com-error)  
[How email sending works in Amazon SES - Amazon Simple Email Service](https://docs.aws.amazon.com/ses/latest/dg/send-email-concepts-process.html)  
[Amazon SES and deliverability - Amazon Simple Email Service](https://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-concepts-deliverability.html)

Email from MAILER-DAEMON@amazonses.com: Delivery Status Notification (Failure)

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