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# 📨Mail Aliases: What & Why

**Mail aliases** are alternate email addresses that deliver to the same mailbox.

They let you:

* **Filter & organize** incoming mail
* **Track** where sign-ups/newsletters come from
* **Protect** your real address
* **Quickly disable** an address by removing the alias

Alias methods vary by provider—below are some common tricks and platform specifics.

---

## Gmail Tricks

### 1. “Plus” Subaddressing ➕

Gmail ignores anything between your username and the `@`.

* **Format:** `yourname+tag@gmail.com`
* **Example:**

```
  realname@gmail.com
  realname+shopping@gmail.com → goes to realname@gmail.com
  realname+work@gmail.com → goes to realname@gmail.com
```
* **Use Cases:**

* Newsletter sign-ups: `you+newsletter@gmail.com`
* Automated filtering: label all `you+shopping@…` as “Shopping”

### 2. “Dot” Ignoring • • •

Gmail also ignores periods in the username part.

* **Any of these are equivalent:**

```
  your.name@gmail.com
  y.ourn.ame@gmail.com
  yourname@gmail.com
```
* **Trick:** Use different dot-patterns to test where spam or leaks originate.

---

## Other Consumer-Level Aliasing

* **Fastmail & ProtonMail:** support full subaddressing (`+tag`) and custom domains.
* **Catch-all Addresses:** set up `*@yourdomain.com` to route everything to one mailbox (great for testing but beware of spam).

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## Enterprise Use Cases

### Microsoft Exchange & Office 365

* **Proxy Addresses (Aliases):**

* You can assign up to **400** SMTP proxy addresses per mailbox (including the primary address).
* Supports multiple domains (e.g., `user@primary.com`, `user@aliasdomain.com`).
* **How to Add an Alias (Exchange Admin Center):**

1. Open **Exchange admin center** → **Recipients** → **Mailboxes**.
2. Select the user and click **Email address**.
3. Click **+ Add email address**, choose **SMTP**, and enter the new alias.
4. Save changes.
* **Office 365 (Microsoft 365) Portal:**

1. Go to **Users** → **Active users**.
2. Select user → **Manage username and email**.
3. Under **Aliases**, click **Add alias**, enter it, then **Save**.
* **Distribution Groups & Shared Mailboxes:**

* Use when you need multiple people to receive mail to a single address (e.g., `support@`, `sales@`).
* Shared mailbox quotas and permissions managed separately from user mailboxes.

### Other Enterprise Platforms

| Platform | Alias Limit | Notes |
| ---- |
| Google Workspace | essentially unlimited `+` subaddresses¹ | No GUI for SMTP proxies; use plus addresses or domain aliases |
| Office 365 | 400 proxy SMTP | GUI and PowerShell support for bulk operations |
| Zimbra | unlimited | Supports both alias and forwarding rules |
| Postfix (self-host) | unlimited | Configure `virtual_alias_maps` in `main.cf` |

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## Best Practices & Tips ✅

1. **Use consistent tags**

* e.g., `user+clientA@…`, `user+clientB@…`
2. **Automate filtering**

* In Gmail/Workspace, create filters based on `+tag` → auto-label/archive.
3. **Monitor alias usage**

* If an alias starts receiving spam, you can disable it or add it to a blocklist.
4. **Document aliases in your KB**

* Keep a table of active aliases and their purpose, especially in larger orgs.

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¹ Plus-addressing in Workspace can’t be disabled and works across all Google services.

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