nopcommerce 3.7 still sending out duplicate email when using multiple worker process

Also our nop 3.7 sometimes sent duplicate email (both in sending newsletter and normal email). In our system, this issue is related to the size of the table QueuedEmail. It was 1.8GB. After dropping all the content, all it's fine.

We're having the same issues I just upgraded to 3.80 and it's still sending out duplicate emails. I've enabled MultipleInstancesEnabled and I've also enabled RedisCache and it still hasn't resolved out issue. We were running 4 instance before and getting 4 emails sent at a time. Now we have 2 server instances and the rest are alias which workout better. We have 2 different domains so we kind of need at least 2 instances of the server running. The problem comes and goes but email blasts are the worst, it will sends duplicates every time.(Always only 1 email in the queue also) I'm thinking of overriding the email service and make it send only if it comes from StoreId from the server I want to send from.

Keep in mind that Web Farm is different from Web Garden.

Nopcommerce supports multiple instances since they are on different servers (Web Farm).

If you are increasing IIS Pool processes, this is called web garden, that is not supported yet.

More info: https://abhijitjana.net/2010/10/01/what-is-the-difference-between-web-farm-and-web-garden/