Setting Up TrekMail IMAP and SMTP in Microsoft Outlook

Outlook works well with TrekMail over IMAP. There are two routes: auto-setup (works when your domain has the autodiscover CNAME live and is the right experience for most users) and manual setup (when auto fails or you want explicit control). This guide covers both, plus the Outlook-specific things that catch people out.

Outlook versions covered

Each Outlook version has slightly different UI but the same underlying settings:

• Outlook for Windows (Classic): the older perpetual-licence Outlook (Outlook 2016, 2019, 2021).
• New Outlook for Windows: the rebuild Microsoft is rolling out to replace classic. Different UI, fewer settings exposed.
• Outlook for Mac: the macOS app.
• Outlook on the web (OWA): outlook.office.com or outlook.live.com. Note: OWA is part of Microsoft 365 / Outlook.com. You can't add an external IMAP account to OWA in many cases, it's primarily for Microsoft-hosted mail.
• Outlook Mobile (iOS/Android): the official Outlook app on phones.

Auto-setup (recommended)

If your domain is configured for autodiscover, Outlook may set itself up with just your email and password:

1. Open Outlook.
2. File → Add Account (Classic Outlook). In New Outlook: Settings (gear icon) → Accounts → Email accounts → Add account. In Mobile: Settings → Add Mail Account.
3. Enter your TrekMail email address (e.g. alice@yourcompany.com).
4. Click Connect (or Continue).
5. If Outlook completes setup without a certificate warning, let it finish.
6. Enter your mailbox password when prompted (this is the password for the mailbox, not your TrekMail dashboard password).
7. Done. Outlook connects and starts syncing.

Do not accept a security warning. If Outlook cannot complete automatic setup cleanly, choose manual setup and copy the settings shown in Apps & devices for the mailbox.

If auto-setup fails, fall back to manual setup below. Your account administrator can check the domain's autodiscover DNS record separately.

Manual setup (Classic Outlook for Windows)

1. File → Add Account.
2. Enter your email address.
3. Click Advanced options → check Let me set up my account manually → Connect.
4. Choose IMAP as account type.
5. Incoming Mail: copy the incoming server, port, and security option from Apps & devices.
6. Outgoing Mail: copy the outgoing server, port, and matching security option from Apps & devices.
7. Login Information:
   • Username: your full email address (e.g. alice@yourcompany.com)
   • Password: your mailbox password
   • Check "Require logon using Secure Password Authentication (SPA)" should be OFF (we use standard password auth over TLS).
8. Click Next → Connect.

Manual setup (New Outlook for Windows)

The New Outlook hides several manual-setup options compared to Classic. Recent versions have started exposing them again:

1. Settings (gear icon) → Accounts → Email accounts → Add account.
2. Enter your email address.
3. If autodetect fails (it tries autodiscover first), you'll get an option to Set up manually.
4. Choose IMAP.
5. Enter the same settings as in the Classic Outlook section above.

If New Outlook refuses to let you add a non-Microsoft account at all (some early builds had this restriction), use Classic Outlook for the moment or wait for a Microsoft update.

Manual setup (Outlook for Mac)

1. Outlook menu → Settings → Accounts → + → Add Email Account.
2. Enter your email and click Continue.
3. If autodiscover fails, click Choose the provider when prompted.
4. Choose IMAP.
5. Fill in your full email address and mailbox password, then copy the incoming and outgoing server details from Apps & devices.
6. Click Add Account.

Manual setup (Outlook Mobile, iOS / Android)

1. Open Outlook app → Settings (top-left/right gear icon) → Add Mail Account → Add Email Account.
2. Enter your email. Tap Add Account.
3. If asked for account type, choose IMAP.
4. Enter your full email address and mailbox password, then copy the incoming and outgoing server details from Apps & devices.
5. Tap Sign in.

Outlook Mobile is good at autodiscover; most users never see the manual fields.

Common problems

"Outlook keeps asking for password" loop

The single most-reported Outlook problem with any IMAP account. Causes, ordered by frequency:

• Wrong password. You're typing your TrekMail dashboard password, not the mailbox password. They're different, see Forgot Your TrekMail Password? for the distinction.
• Wrong username format. Outlook needs the full email address as the username, not just alice. Some older Outlook builds default to local-part; correct it manually.
• Cached old credentials. When you've changed the mailbox password recently, Outlook may keep retrying the old one from credential cache. Windows: Control Panel → Credential Manager → Windows Credentials → remove only entries that match the server names shown in Apps & devices. Restart Outlook. On Mac: Keychain Access → search for those server names and remove only the matching entries. Outlook will prompt for the password fresh next time.
• SPA option turned on. Make sure "Secure Password Authentication" is OFF in IMAP/SMTP advanced settings. We use plain auth over TLS, not SPA.

"Cannot send mail. The connection to the server failed."

• Port 465 may be blocked by your local network. Try port 587 with STARTTLS, or another network. If both supported ports are blocked, ask your network administrator.
• Wrong outgoing server hostname: copy it again from Apps & devices rather than guessing from the email domain.
• Wrong encryption mode for the port, port 465 = SSL/TLS, port 587 = STARTTLS. Mixing them up causes immediate failure.

"Folders aren't syncing" or "missing folders"

• Right-click your account in the folder list → Update Folder List (or "IMAP Folders" → Query and Refresh).
• Check your IMAP advanced settings for a Root folder path value. It should be empty. If somehow set to "INBOX" or similar, some folders are hidden, clear the field, then update folder list.
• Some Outlook builds have a "Show only subscribed folders" toggle. Turn it off in IMAP advanced if you're missing folders.

"I keep getting Outlook security alerts about the certificate"

Re-copy the server values from Apps & devices. A mistyped server name or the wrong TLS option can cause this warning. Do not continue past it. If the values are correct, update Outlook and Windows, then ask your IT team whether a corporate network is intercepting encrypted mail traffic.

"I migrated from POP and want to switch to IMAP"

POP downloads emails to your device only. IMAP keeps them on the server. The switch isn't automatic:

1. Add a new account in Outlook using the IMAP settings above. Don't delete the POP account yet.
2. Wait until the IMAP account syncs (downloads the existing mail from the server).
3. Compare folder contents, emails received before the switch may not be in the IMAP folder list because POP downloaded them and removed them from the server.
4. Move (drag-and-drop) any emails from the old POP folders into the new IMAP folder structure. They re-upload to TrekMail and become visible everywhere IMAP works (webmail, phone, etc.).
5. Delete the POP account once you've moved everything.

If you used POP with "leave messages on server", this is much easier, the server still has everything, you just rebuild the IMAP folder structure.

"Sending is slow / sometimes fails"

Outlook sometimes batches outgoing messages and sends them all at once. If you have a hourly SMTP rate limit (see Sending Limits per Plan), this can hit the limit. Reduce the send-batch size in Outlook's settings if you're consistently bouncing off the rate cap.

"Sent items aren't appearing on TrekMail webmail"

Outlook saves Sent items in a "Sent Items" folder. TrekMail uses "Sent". Outlook should map the two automatically via the IMAP SPECIAL-USE capability, but on older builds this fails:

• Outlook → Account Settings → Change → check that the Sent Items Folder is set to "Sent" (the server-side folder), not the local "Sent Items" client folder.
• Alternatively, configure Outlook to use the same Sent folder TrekMail does (Sent), which avoids the mismatch entirely.

Performance and battery tips

• For the desktop Outlook, the default sync interval works. For mobile, the default is "Push". This drains battery if your mailbox is busy. Switch to "Every 15 min" in Outlook Mobile settings if battery is a concern.
• Outlook keeps a local cache of all your mail. For very large mailboxes (50GB+), this can slow Windows down. Use the "Mail to keep offline" slider to limit cache to 6 months / 1 year / etc.
• Avoid watching every folder in IMAP IDLE mode. Watching more folders can make Outlook open more simultaneous connections, so limit this to Inbox and a few important folders if you approach your plan's connection limit.