Creating and Managing Aliases

This guide walks you through adding aliases to a mailbox, toggling their settings, sending from them, and removing them when no longer needed.

Adding an alias

1. Go to Mailboxes and click Settings next to the mailbox.
2. On the Aliases tab, click New Alias.
3. Enter the local part (the part before @) and select a domain from the dropdown.
4. Choose your options:
   • Allow receiving — incoming mail to this alias will be delivered to the mailbox (on by default).
   • Allow sending from this address — lets you use this alias in the "From" field when sending emails (off by default).
5. Click Add Alias.

The alias starts working immediately — no DNS changes or server restarts needed. Try it by sending a test email to the alias from another account.

Naming rules

• Lowercase letters, numbers, dots, hyphens, and underscores only.
• Maximum 64 characters.
• Must be unique across your entire account — can't match an existing mailbox, another alias, or a system address on the same domain.
• Examples of valid aliases: info, sales-team, john.doe, billing_dept, contact.us
• Examples of invalid aliases: Info (uppercase), sales team (spaces), hello@world (@ not allowed)

Cross-domain aliases

The domain dropdown shows all active domains on your account. You can create an alias on a different domain than the mailbox. For example:

• Mailbox: john@brand-a.com
• Alias: sales@brand-b.com

All mail to sales@brand-b.com arrives in John's inbox. This is useful when you manage multiple brands or client domains from a single account.

Both domains must be active and verified in TrekMail. If a domain's DNS isn't configured, it won't appear in the dropdown.

Enabling and disabling aliases

Each alias has two independent toggles:

• Enable / Disable — Controls whether the alias is active. A disabled alias stops receiving and sending mail entirely. Use this to temporarily suspend an alias without deleting it.
• Send: On / Off — Controls whether you can use this alias as a "From" address when sending emails. This has no effect on receiving.

Click the corresponding button next to any alias to toggle it. Changes take effect immediately — within seconds on the mail server.

When to disable vs. delete

• Disable when you might need the alias again later. The address stays reserved and no one else can claim it. Mail sent to it will bounce with "user unknown."
• Delete when you're sure you no longer need it. The address is freed up and can be reused by any mailbox on the account. Mail sent to it will bounce (or be caught by catch-all if enabled).

Sending from an alias

When "Allow sending" is enabled for an alias, you can send emails using that address as the sender. Recipients see the alias address, not your primary mailbox address.

In TrekMail webmail

1. Log in with the primary mailbox address and mailbox password. An alias does not have its own password or separate login.
2. Confirm that the administrator enabled Allow sending from this address for the alias.
3. Open your avatar menu → Settings → Sending addresses.
4. The active send-enabled alias appears automatically. Open its card to set its display name, optional Reply-To, and signature.
5. In a new message, choose the alias from the From menu.

You do not manually create or delete the automatic alias cards in webmail. The mailbox address and its active send-enabled aliases are the source of truth. Turning off the alias's send permission removes it from the From list without stopping receipt if Allow receiving remains enabled.

Under Settings → Sending addresses, you can also make the alias the default for new messages. For replies, choose either Address that received the message or Default address for new messages. The first option checks the original delivery address so a reply sent to an alias can automatically use that alias in From.

If this alias forwards into a connected Gmail, Outlook, or other inbox, click Add a From address to link the alias to that inbox. See Send From a Business Address Using Gmail. The same button adds a From address with no inbox behind it, which is what you want when the mail is forwarded in from a provider you have not connected.

In Outlook

1. Open Outlook and go to File → Account Settings → Account Settings.
2. Select your TrekMail account and click Change.
3. Under More Settings → Advanced, you may be able to add the alias as an additional "Send As" address (depends on Outlook version).
4. Alternatively, create a new account in Outlook using:
   • Email: The alias address
   • Username: Your primary mailbox address (e.g., john@company.com)
   • Password: Your mailbox password (same as primary)
   • IMAP/SMTP servers: Same as your primary mailbox

In Apple Mail (macOS / iOS)

1. Open Mail → Settings → Accounts → select your TrekMail account.
2. In the Email Address field, add the alias after a comma: john@company.com, sales@company.com.
3. When composing, click the From field to switch between addresses.

In Thunderbird

1. Go to Account Settings for your TrekMail account.
2. Click Manage Identities at the bottom.
3. Click Add and enter the alias address.
4. When composing, the From dropdown will include the alias.

Via SMTP / other email clients

The general pattern for any email client:

1. Add a new "identity", "persona", or "send as" address in your client settings.
2. Use the same SMTP server and credentials as your main mailbox:
   • SMTP Host: mail.yourdomain.com (or as shown in your domain's Connection tab)
   • Port: 465 (SSL) or 587 (STARTTLS)
   • Username: Your full mailbox address (e.g., john@company.com)
   • Password: Your mailbox password
3. Set the From address to the alias (e.g., sales@company.com).

TrekMail's server checks that the alias belongs to your mailbox and has sending permission. If it does, the message goes out. If not, the server rejects it with a "sender address rejected" error.

Via API or MCP

When sending via the TrekMail Message API (POST /api/v1/messages/send) or MCP tools, specify the alias address in the from field. The system validates that:

1. The alias belongs to the authenticated mailbox.
2. The alias has can_send enabled.
3. The alias is active (is_active = true).

If any check fails, the send is rejected with an error.

Seeing which alias received a message

When an email arrives via an alias, the message includes a Delivered-To header showing the original alias address.

In TrekMail webmail

Open the message's more-actions menu and choose View source. Look for:

Delivered-To: sales@company.com

This tells you the email was originally sent to sales@company.com, even though it ended up in your john@company.com mailbox.

Using filters to sort alias mail

You can create mail filters that sort messages by which alias they were sent to. For example:

• Condition: Header Delivered-To contains sales@
• Action: Move to folder "Sales"

This automatically organizes incoming mail by purpose. See Creating and Managing Filters for step-by-step instructions.

Tip: Create a folder structure like "Sales", "Support", "Billing" and set up one filter per alias. Your inbox stays clean, and you always know which address received each message.

Deleting an alias

1. On the Aliases tab, click Delete next to the alias.
2. Confirm the deletion in the popup.

What happens after deletion:

• Mail sent to that address will bounce with "user unknown" (unless a catch-all is configured for the domain).
• The address is freed up and can be reused — you or another mailbox on your account can claim it.
• If someone has the alias saved in their contacts and sends a message, it will bounce.
• This action cannot be undone. If you need the alias back, you'll have to recreate it.

Before deleting, consider:

• Are there any websites, forms, or business cards using this address?
• Have you shared this alias with clients or partners?
• Would disabling (instead of deleting) be safer until you're sure?

Bulk alias management

If you need to manage aliases for many mailboxes, the REST API and MCP tools are faster than the dashboard:

• API: Use POST /api/v1/mailboxes/{id}/aliases in a loop or batch script to create aliases across multiple mailboxes.
• MCP: Use the create_alias tool to let AI agents set up aliases as part of a larger onboarding workflow.

The API supports idempotency keys, so retries are safe — creating the same alias twice won't produce duplicates.

Limits

Each plan has a maximum number of aliases per mailbox:

The current usage is shown at the top of the Aliases tab (e.g., "2 of 30"). When you reach the limit, you'll see a message with an option to upgrade.

Trial accounts have an additional safety limit of 5 aliases per mailbox until the first payment is completed.

Common questions

• Can I change an alias address? No — delete the old alias and create a new one. Both actions are instant. The old address is immediately freed up, and the new one starts working right away.

• Does an alias use extra storage? No. Aliases share the same inbox and storage as the parent mailbox. A message sent to an alias counts toward the mailbox's storage, just like any other message.

• Can two mailboxes share the same alias? No. Each alias address must be unique across your entire account. If mailbox A has info@domain.com as an alias, mailbox B cannot use it.

• What happens if I delete the mailbox? All its aliases are deleted automatically. The alias addresses become available for reuse.

• Do aliases work with catch-all? Yes. If a domain has catch-all enabled and an alias exists on that domain, the alias takes priority. Mail to the alias goes to the alias target; mail to unknown addresses goes to the catch-all destination.

• Can I forward mail from a specific alias only? Not directly on the alias. But you can use a mail filter with a condition on the Delivered-To header to forward messages that arrive via a specific alias.

• Do aliases affect deliverability or spam reputation? No. Aliases don't send mail — your mailbox does. The alias is just an address that redirects to the mailbox. Sending reputation is tied to the mailbox and domain, not individual aliases.

• Can I create an alias on a domain I don't own? No. The domain must be added and verified in your TrekMail account. You can only create aliases on domains you control.

• Is there a way to import aliases in bulk? Not yet from the dashboard. Use the API (POST /api/v1/mailboxes/{id}/aliases) or MCP tools for bulk creation.