To what degree can/should you overprovision a mail server?

Michael Sørensen

7/25/24, 1:24 PM

I'm considering setting up a mail server as a side offering to my hosting business. I know that other providers won't "reserve" the disk space for an account (i.e. 15GB for gmail), but to what degree can one overbook the available storage in terms of accounts promised and actual disk space?

1 + 6

hosting

email-server

anx

7/25/24, 1:30 PM

I don't think this can be meaningfully answered without basing the answer on what unspecified time interval you will need, and what time interval you will have (including the worst timing possible), when adding new disk space to both production environment and backup space. What maximum mail size would you like to accept? Will you setup some rate limiting on top of per-user quotas?

Luuk

7/25/24, 1:33 PM

will your "side offering" be "best effort", or "guaranteed delivery/up-time; backup; antivirus/spam checks; ..." ?

ceejayoz

7/25/24, 1:38 PM

Monitor usage and set up alerting. The answer to this will vary enormously depending on your clients.

Esa Jokinen

7/25/24, 1:39 PM

This is both opinion based and about capacity planning, and neither is a good fit for this Q/A site. But maintaining a mail service is hard: your customers start having issues both with inbound spam and outbound mail getting on block lists. It is probably best to leave this for the professional email providers.

HBruijn

7/25/24, 3:35 PM

Offering *"unlimited"* or severely over-provisioned email storage was an option back in the day when a hosting provider could get away with only offering POP3 access and a single INBOX. Most POP3 clients defaulted to deleting all messages from the server after retrieval and effectively actively used mailboxes only stored a handful of unread messages but were empty most of the time and your worst concern were forgotten/abandoned mailboxes that could grow indefinitely.

HBruijn

7/25/24, 3:36 PM

With the advent of webmail and most user consuming their email from multiple devices, people don't accept POP3 anymore . They'll leave all their mail on the server. Unless you actively purge old messages expect that people will only start cleaning up their mailbox once they start getting "quota exceeded" warnings. Eventually you'll need to actually deliver close to what you sold. How quickly that happens depends on your users, but might be anticipated with good monitoring and capacity management practices. Don't forget how much additional storage for replication and/or backup will be needed.

Score:5

Server

anx

7/25/24, 1:42 PM

Consider not over-provisioning at all, initially.

Understand that some features, such as indexed full text search, can significantly increase your storage overhead beyond the basic "how many GiB of mail are accepted in one box". These days spam filters like to have a substantial "working area" as well, your server could at times be working on 100 junk submissions at the same time, none of which are eventually accepted, yet still should not impede your ability to process legitimate mail flows.

Slap a few cheap 2TB disk into your RAID, and set a reminder to check after 50, 100 and 200 users are registered. Mailboxes generally grow indefinitely, so there is no way you are not making storage extensions and scaling (in both primary storage and emergency recovery) a key part of the operation anyway.

I do not believe doing email as a side offer can be remotely profitable these days: The involved mechanisms for a pleasant experience just became too complex - yet not overly depending on user count - to justify anything but operating professionally, specialized & at scale. Hence, what you spend on the first 200 users is not really relevant. Besides, the first few users will not hit the disk anyway, because everything fits in RAM, so you can start cheap and buy proper solid state storage later, when you do know actual usage patterns and growth over time.

+ 1

Michael Sørensen

7/31/24, 12:12 PM

Thank you for your answer. I will reconsider my idea, or perhaps find a reasonable reseller of email services.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: To what degree can/should you overprovision a mail server?

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.