We’ve described twelve mail clients in the knowledge base. Which one fits you? Here’s the recommendation in plain terms — what our team uses itself, what we recommend to customers, what we avoid for privacy or stability reasons.
Recommendation by platform
macOS
| Choice | When |
|---|---|
| Apple Mail ⭐ | The default. Stable, integrated into macOS, IMAP plus built-in CalDAV/CardDAV sync with Apple Calendar and Contacts. The right choice for most Mac users. |
| Thunderbird | If you want open source, identical across platforms, or need specific plugins. |
| Outlook for Mac (classic) | If you have an Office 365 license and are used to the Outlook look and feel. |
| eM Client | If you want an Outlook-ish look but no Microsoft. Commercial, ~€60 one-time. |
| ❌ Outlook for Mac (new) | Web view, mail gets routed through Microsoft servers — avoid. |
Windows
| Choice | When |
|---|---|
| Outlook (classic, 2019/2021/365) ⭐ | The business standard. Stable via IMAP; calendar and contacts via the CalDav Synchronizer plugin. |
| Thunderbird | Open source, free, cross-platform, a good choice if you have no Office. |
| eM Client | If Outlook-ish but without an Office license. ~€60 one-time. |
| ❌ Windows Mail app | Being phased out (by Microsoft itself), replaced by the “new Outlook”. Not for serious use. |
| ❌ Outlook (new, Win 11) | Web view, mail routed through Microsoft servers — avoid. |
| ❌ Windows Live Mail | Unsupported since 2017, switch urgently. |
Linux
| Choice | When |
|---|---|
| Thunderbird ⭐ | The default. Identical across platforms, huge community, all the features. |
| Evolution | If you’re on a GNOME desktop and want Outlook-style integration. |
| KMail / Kontact | If you’re on KDE Plasma and want deep KDE integration. |
| Geary | Minimal mail client (GNOME), few features — for purist use. |
iOS (iPhone, iPad)
| Choice | When |
|---|---|
| Apple Mail ⭐ | The default. IMAP plus CalDAV/CardDAV, set up in one step via .mobileconfig profile. iOS fetches new mail at intervals (Fetch New Data), not instantly. Recommendation for most. |
| Spark | Third-party, slick, but mail content gets routed through the Spark cloud — check the privacy angle. |
| Outlook for iOS | Works, but cloud routing via Microsoft. |
| ❌ Gmail app on iOS | Cloud routing via Google — careful. |
Android
| Choice | When |
|---|---|
| K-9 Mail / Thunderbird Mobile ⭐ | Open source, direct IMAP access, IMAP IDLE — new mail arrives near-instantly. Combined with DAVx⁵ for calendar/contacts = the best GDPR-friendly setup. |
| The manufacturer’s stock app (Samsung, Xiaomi, etc.) | Preinstalled, IMAP straight against Mailcow. Calendar and contacts come via DAVx⁵. |
| Outlook for Android | Works, but cloud routing — see the note. |
| ❌ Gmail app (with Gmailify) | Gmailify routes through Google — with an explicit “configure manually” it goes direct, but careful. |
Recommendation by use case
”I just want to receive and send mail, nothing else.”
- Mac/Win: Apple Mail or classic Outlook.
- Linux: Thunderbird.
- Smartphone: Apple Mail (iOS) or the manufacturer’s stock app (Android).
”I want mail, calendar and contacts in one account — in sync everywhere.”
The path is the same on every platform: IMAP/SMTP for mail, CalDAV/CardDAV (SOGo) for calendar, contacts and tasks. There is no extra protocol for smartphones.
Straight talk on push: we don’t offer real Exchange push. Clients like Thunderbird or K-9 keep a connection to the server open via IMAP IDLE — new mail arrives near-instantly. iOS Mail, by contrast, only fetches IMAP accounts at intervals (adjustable under Settings → Mail → Accounts → Fetch New Data); a few minutes of delay is normal there.
Here’s what that looks like per device:
- iOS: Apple Mail via
.mobileconfigprofile — sets up mail, calendar and contacts in one step. See Setting up Apple Mail (iOS). - Android: K-9 / Thunderbird Mobile for mail, DAVx⁵ for calendar and contacts.
- macOS: Apple Mail plus Apple Calendar/Contacts — CalDAV/CardDAV is built in.
- Windows: classic Outlook plus CalDav Synchronizer.
- Linux: Thunderbird — calendar and address book speak CalDAV/CardDAV natively.
With 2FA active, you need an app password for IMAP/POP3/SMTP — see App passwords.
”I want open source, no cloud routing, maximum privacy hygiene.”
- Desktop (all platforms): Thunderbird with IMAP/SMTP, plus server-side Sieve filters in SOGo.
- Android: K-9 / Thunderbird Mobile + DAVx⁵.
- iOS: Apple Mail with IMAP, calendar and contacts via CalDAV/CardDAV.
”I already use Office 365 / Microsoft anyway.”
Classic Outlook (for Mac and Win) is the natural choice. Even if you primarily use Microsoft 365, your Mailcow account with us gets set up in Outlook as a second IMAP account alongside it.
”I’m migrating from Microsoft 365 or Google.”
During the migration, use the app you’re used to — Outlook for 365 migrations, the Gmail app for Google migrations. Once the migration is done, you can switch to another app.
Migration guides: Migrating from Microsoft 365 and Migrating from Google Workspace.
”I share the mailbox with others — newsletters, a shared role address.”
Most apps let you create multiple identities per account. Apple Mail, Outlook and Thunderbird all do this well. For more complex workflows: set up Mailcow aliases (see Aliases and catchall) and use them as an additional identity in the mail client.
What we use internally
Full transparency — what our team uses for its own mail:
- Mac workstations: Apple Mail with IMAP, calendar and contacts via CalDAV/CardDAV against our internal Mailcow.
- iPhone: Apple Mail with IMAP, calendar and contacts via CalDAV/CardDAV — set up through the
.mobileconfigprofile. - Linux workstation: Thunderbird with IMAP + local CalDAV/CardDAV sync.
- Android (private): K-9 / Thunderbird Mobile + DAVx⁵.
We like apps that talk to the server directly, without a third-party cloud in the routing path. Hence the choices above.
Privacy trade-offs at a glance
| App | Routes through a third party? |
|---|---|
| Apple Mail (Mac/iOS) | No, direct |
| Classic Outlook (Win/Mac) | No, direct |
| Outlook (new, Win 11) | Yes, Microsoft |
| Outlook for Mac (new) | Yes, Microsoft |
| Outlook app on mobile | Yes, Microsoft |
| Gmail app with Gmailify | Yes, Google |
| Gmail app with “manual” | No, direct |
| Thunderbird | No, direct |
| K-9 / Thunderbird Mobile | No, direct |
| eM Client | No, direct |
| Stock app on Android (Samsung etc.) | No, direct |
| Spark | Yes, Spark cloud |
| Newton | Yes, Newton cloud |
Recommendation: avoid apps with cloud routing if GDPR and “no US Cloud Act” matter to you.
Frequently asked questions
Which app is the fastest? Apple Mail and classic Outlook are extremely performant — they’re native apps. Web views (new Outlook) and some cross-platform apps (Electron-based) are more sluggish.
Which app has the best spam filter? Spam filters run server-side on our Mailcow — client apps merely use it. So a client-side spam filter isn’t the deciding factor. What matters: that the app shows the Junk folder cleanly and doesn’t constantly mislabel mail as spam.
Which app is the most secure? Security comes from: TLS configuration (all apps mentioned here support TLS 1.2+), no third-party routing, app updates. Open-source apps like Thunderbird have the advantage that the source is inspectable.
Multiple apps in parallel on one device? Works fine. They all use IMAP, they all see the same mail. What one marks as read is read in the other too.
Why does new mail arrive delayed on the iPhone? iOS Mail only fetches IMAP accounts at intervals — an Apple decision, not a server problem. You set the interval under Settings → Mail → Accounts → Fetch New Data. If near-instant delivery matters to you: Thunderbird on the desktop and K-9 / Thunderbird Mobile on Android keep the connection open via IMAP IDLE — mail lands there with practically no delay.
Which app can do the most? Classic Outlook is the feature champion (1000+ features). Thunderbird comes close (with plugins). Apple Mail is minimalist — which many see as an advantage.
What if none of the recommendations fit? The server data is in the server data reference — you can hook up practically any IMAP mail client. If you want to try a specific app and get stuck: open a ticket, we’ll help.
What’s next
First login as domain admin in the Mailcow GUI
After ordering your mail server plan, you get access to the Mailcow GUI. Here's an overview of what you see as domain admin and where to find what.
Creating and editing mailboxes, setting quotas
How to create new mail addresses as domain admin, assign storage quotas, change passwords and delete mailboxes again.
Setting up aliases and a catchall
Route several mail addresses into one mailbox — info@, kontakt@, presse@ all in a single inbox. Plus a catchall for every typo address.
Creating app passwords for mail clients
With 2FA active, Outlook, Apple Mail and friends need an app password instead of your main password. How to create them, revoke them and avoid password chaos.