IMAP & SMTP Settings for All Clients

The easiest option is Apps & devices, which gives you guided steps and the exact server names for the selected mailbox. Use the reference below when an app asks you to enter the details manually.

Who this is for

• Users configuring a desktop or mobile email client.
• Developers configuring a script to send email.

1. Incoming Mail (IMAP)

Use these settings to receive email.

Note: TrekMail does not support POP3. Use IMAP to keep folders and message state synchronized across devices.

2. Outgoing Mail (SMTP)

Use these settings to send email.

A verified White Label setup can show branded IMAP and SMTP hosts. Use those values when they appear; do not replace them with a hostname guessed from the mailbox address. Port 587 with STARTTLS is the supported SMTP alternative when port 465 is blocked.

IMAP Connection Limits

To ensure fair resource usage and server stability, TrekMail enforces concurrent IMAP connection limits based on your subscription plan.

• Per IP: Maximum simultaneous connections from a single IP address (e.g., your home network).
• Total: Maximum simultaneous connections across all devices and locations.

What happens if I exceed the limit?

Your email client will receive a "Maximum connections exceeded" error and won't be able to establish new IMAP connections until existing ones are closed.

Tips to avoid connection limits

• Close unused email clients: If you have multiple devices, close email apps you're not actively using.
• Check client settings: Some email clients open excessive connections. Configure them to use fewer simultaneous connections.
• Upgrade if needed: If you regularly hit the limit with normal usage, consider upgrading to a higher plan.

CalDAV / CardDAV (calendar and contacts)

In addition to IMAP/SMTP for mail, TrekMail exposes calendar and contacts over CalDAV/CardDAV. This is what your phone or desktop calendar app uses to sync events and contacts.

For platform-specific guides see: Apple · iPhone/iPad · Android · Thunderbird · Outlook (caveats).

Passwords and app passwords

Each regular mailbox has one of two sign-in modes for mail apps, including calendars and contacts. Apps & devices shows which one applies to the selected mailbox. Shared mailboxes have no app passwords or mode; members open them with their own mailbox credentials.

New mailboxes follow Account settings > New mailboxes > Mail apps need app passwords, which is on by default. Changing it never switches existing mailboxes. When creating a single mailbox in the dashboard, Mail apps sign in with lets you choose differently.

• Where to create one: in webmail under Settings > App passwords, or in the dashboard under Mailboxes > your mailbox > Security > App passwords (anyone allowed to set the mailbox password can do this). In Apps & devices, a mailbox that needs an app password also shows a Create an app password link.
• What it looks like: 16 letters, shown only once and grouped in four blocks of four. Spaces and capital letters do not matter. A mailbox can have up to 25 active app passwords, so give each device its own.
• Where it works: IMAP, SMTP on ports 465 and 587, ManageSieve, and CalDAV/CardDAV. It never opens the new webmail or the dashboard. New webmail uses the mailbox password, plus a code if two-factor authentication is on. Classic webmail uses an app password for App passwords only mailboxes. Two-factor authentication protects webmail sign-in only; mail apps and classic webmail never ask for a code.
• If the app shows this error: "Sign-in failed. This mailbox accepts app passwords only: create one in webmail under Settings > App passwords." The mailbox refused its mailbox password. Create an app password and enter it in the app instead. Some apps only report a generic password failure, so check the mode in Apps & devices too.
• When app passwords stop working: Replace ends the old secret immediately; Revoke stops that password. An account admin setting a new mailbox password in the dashboard, API, or an AI agent revokes all app passwords. A user's own password change in webmail keeps them unless they select Also revoke all app passwords (off by default). Password reset or recovery, sign-in suspension, conversion to a shared mailbox, and moving to Recently deleted revoke all of them. Restoring a mailbox does not restore its app passwords. A device whose app password was replaced or revoked needs a new one.

For the full guide, see Mail app passwords.

Important Notes

• Username: Always use the full email address. Just alice will fail.
• Passwords: Use an app password or the mailbox password, as described above, never your TrekMail account password for the dashboard.
• Custom SMTP routing: If your plan does not include managed sending, configure your provider under the domain's SMTP settings first. Your email app still connects to the outgoing TrekMail or branded host shown in Apps & devices with the same password it uses for IMAP. TrekMail applies the private provider route behind the scenes; do not place the provider's secret credentials in an end user's email app.