Multiple Emails Wrongly Being Sent to Recipients

I am using Universal Email - WA_Email.php version 1.19

PROBLEM: When sending to a large recordset of 6,299 recipients, many times multiple email are being sent to the same email recipient sometimes 2-3 times.

The recordset only contains unique email addresses so there are no duplicates, yet 2-3 emails are sent. The time difference between the first send and the third send is about 20 minutes.

I am using SendGrid to send the emails.

Any idea what could be causing this?

I'd try adding email logging and see if it is trying to send multiple or if the SMTP server is mistakenly sending more than one email. You could also add a unique id or timestamp to the email body to test if the same email is being delivered twice or if they are different emails entirely.

If the email log doesn't report the script sending more than one copy, or the unique id is the same in the multiple emails, then the issue isn't with your php code itself. The issue is with the SMTP server.

I have heard that some SMTP servers can have a queuing issue that causes repeated emails to send when receiving a large batch. You might try decreasing the batch size or adding a wait between message sending to address this issue.

If you google "smtp sending repeated email", you will see that this is a common issue on some servers and can maybe be fixed by your hosting provider.

Thanks! I do have email logging enabled. It looks like it is being sent multiple times. Attached is an example of a single recipient being sent the same email 3 times.

Does this mean SendGrid is the problem?

That implies your recordset is returning more than one result. What is the query you are using?

SELECT * FROM mail_list

attachment shows structure

Is it possible people are pressing "send" more than once? I see the emailID has a goap of 6,000 between the first and second email, but only a gap of 270 between the second two. How is the email initiated? Maybe that is happening more than once.

That's what I wondered also.

There is a standard Submit button but I'm using Progress Bar so hopefully it wouldn't be possible to click Submit more than once.

The trigger is:

if (isset($_POST["email_flyer_list_button"]) || isset($_POST["email_flyer_list_button_x"])) { //WA Universal Email

The first two are 23 minutes apart... the last one is only 1 minute and 15 seconds later.

It still doesn't seem like that would be a second press of the button. Maybe log the start of sending emails to identify if it is trying to send twice somehow.