I originally asked this question on AskUbuntu, but I haven't gotten any replies so I figured I'd also ask here.
I am looking to set up an e-mail server with Ubuntu Server, although I am open to alternate operating systems if you have any suggestions that may perform better for my use case. I will have some 19,000+ devices using it to send and receive e-mail. The majority of these devices will probably not be heavily used, as only a few of our clients use the e-mail feature in these devices.
Based on the recommendation of another StackExchange user, I will likely be setting up virtual mailboxes for these devices to cut down on resource usage.
My planned software stack for the mail server will be Postfix, Dovecot, and MySQL. If there are alternatives that would perform better for my use case, please let me know.
The current usage data I have from our old system shows about 14GB of data across 7,684 messages received and 22GB of data across 11,321 messages delivered per week, adding up to around 56GB across 30,736 messages and 88GB across 45,284 messages received and delivered per month, respectively. As a rough estimate, I would say that the server will probably be sending/receiving around 100 to 200 GB across around 100,000 messages per month.
I do not need a large amount of storage per mailbox. The devices receiving mail will only be looking at the messages once to parse them for simple text-based commands. Sent mail does not need to be stored on the server at all, and received mail will be deleted from the server as soon as it's processed by the device.
Based on these figures, I would like to know what the minimum system requirements would be for the server to be able to handle this volume of messages/data smoothly.