The Spark Team
Smart. Focused. Email.
Fast, cross-platform email designed to filter out the noise - so you can focus on what's important.
Definition
💡Mail server: the computer (or cluster of computers) that actually stores, sends, and receives your email, running quietly behind whatever app you use to check it. People also call it an email server, same thing, just a different name. Either way, it's the machine doing the real work every time you hit send.
TL;DR: A mail server is the behind-the-scenes computer that handles your email. Your inbox app (Gmail, Outlook, Spark) is just how you access it.
What does a mail server actually do?
You hit send, and a few seconds later, your message lands in your coworker's inbox. Nothing exciting, right? But a fair amount happened in that gap.
Your email left your device, reached a mail server, got handed off (sometimes through a couple more servers) to your coworker's server, and sat there until their client checked in and pulled it down. Storing, routing, and delivering every message: that's the mail server's whole job.
Every account you've ever had, personal Gmail, work Outlook, a custom address on your own domain, connects to a mail server somewhere. You almost never notice it, because a good email client like Spark handles the connection automatically the moment you sign in. The less you notice your mail server, the better it's working.
You're relying on it more than you'd guess, too. Statista found that people worldwide will send around 392.5 billion emails a day in 2026, and every one of those touches a mail server.
You don't manage your mail server day to day. But when something breaks (an account won't sync, a new address won't connect), that server is usually where the actual problem lives.
How SMTP, IMAP, and POP3 fit in
Here's where people get mixed up. A mail server isn't one thing doing one job. Picture an office building, where SMTP, IMAP, and POP3 are separate departments handling separate tasks.
The SMTP server handles outgoing mail, relaying it toward its destination, sometimes through several servers, as Cloudflare's SMTP explainer lays out. IMAP keeps messages stored on the server and synced across every device you own. POP3 is older and simpler: it downloads mail to one device and, traditionally, deletes it from the server after.
You don't need protocol specs to use email well. But knowing the difference matters the one time you're troubleshooting: is your outgoing mail stuck, or is this a sync problem? That question usually tells you which protocol, and which server, needs attention.
Where to find your mail server settings
Most of the time, you'll never see these settings. Signing in with your email and password, or through Google or Microsoft's sign-in flow, handles everything automatically. Setting up a custom domain or fixing a stuck connection is different. That means digging up the actual hostnames.
In Gmail:
- Click Settings (gear icon, top right), then See all settings
- Open the Forwarding and POP/IMAP tab
- Gmail's IMAP server is imap.gmail.com on port 993; its SMTP server is smtp.gmail.com on port 587 or 465
In Outlook:
- Go to Settings, then Mail, then Sync email (called Forwarding and IMAP on some versions)
- Outlook.com's IMAP server is outlook.office365.com on port 993; its SMTP server is smtp-mail.outlook.com on port 587
In Spark:
- Go to Settings > Accounts > Add Account; if standard sign-in doesn't work, look for manual setup
- On Mac and Windows, click Additional Settings; on iOS it’s set up manually; on Android, tap Additional Settings
- That's where you'll type in the incoming and outgoing server addresses and ports by hand
Spark's setup skips this step for most popular providers entirely. You'll only need manual settings for custom domains, older work systems, or a handful of niche providers.
When mail server details actually matter
Setting up a custom domain. Run your own email domain instead of a Gmail or Outlook address, and you'll need the exact hostname from whoever hosts it.
Troubleshooting sync problems. Messages missing on your phone but sitting fine on your laptop usually points to an IMAP issue, not a lost email.
Switching email clients or providers. Moving accounts sometimes means re-entering server details by hand, especially for work accounts that skip one-click sign-in.
Most people go years without touching any of this. And that's kind of the point: a good mail server, paired with a good email client, should stay invisible.