KoltrixPlus addressing and aliases: how to use them well
Plus addressing and aliases give you many addresses from one inbox. Learn how each works, where sites break them, and when to pick one over the other.
On this page(10 sections)
- What plus addressing is
- What an alias is
- Side by side
- Where plus addressing works well
- Where plus addressing breaks
- Websites that reject the plus sign
- Sites that strip the tag
- Duplicate account checks
- The base address is exposed
- Rules can be bypassed
- Where aliases are the better tool
- A practical setup
- Habits that help
- A note on privacy and honesty
- Key takeaways
You only have one mailbox, but you sign up for dozens of services, publish a contact address and run a few side projects. Two small features let a single inbox act like many: plus addressing and aliases. They look similar from the outside and behave very differently once you rely on them.
This guide explains how each one works, what goes wrong in practice and how to choose between them. It is written for individuals and small teams who want fewer surprises, not for mail administrators building a platform.
What plus addressing is
Plus addressing (also called subaddressing or tagging) lets you add a tag after your username, separated by a plus sign. If your address is [email protected], then these all reach the same mailbox:
The mail server strips the tag when it decides where to deliver. The message arrives in your normal inbox, but the original recipient header still shows the tagged address. That is the useful part: you can filter on it, or see which service passed your address along.
Nothing has to be set up in advance. You invent a tag at the moment you need one. Whether it works at all is decided by your mail provider, not by you. Some providers support it by default, some need it switched on and some do not offer it.
What an alias is
An alias is a separate address that you create on purpose and that points to a mailbox. [email protected] can deliver to [email protected] without being a mailbox of its own. Aliases are created by an administrator or by you in your mail settings, and they usually live on your own domain.
The difference that matters: a plus address is a variation of an address you already have, and anyone can see the base address by looking at it. An alias is its own address, and nothing about it reveals the mailbox behind it.
For the bigger picture of how addresses, groups and shared mailboxes differ, see shared inbox vs distribution list vs group alias.
Side by side
| Plus addressing | Alias | |
|---|---|---|
| Created by | You, on the spot | You or an administrator, ahead of time |
| Setup needed | None, if the provider supports it | Yes, one entry per address |
| Reveals your real address | Yes, the base is visible | No |
| Can be switched off | Only by rejecting the tag in a rule | Yes, delete the alias |
| Works for public addresses | Poorly | Well |
| Best for | Tracking and filtering for yourself | Roles and addresses you publish |
Where plus addressing works well
Finding out who shared your address. Sign up to a store with [email protected]. If you later receive spam to that tag, you know where it came from. This is a signal, not proof: the store may have been breached, or the tag may simply have been guessed.
Filtering without extra work. A rule that moves everything sent to [email protected] into a Receipts folder or label takes a minute to write and keeps working. In Koltrix you can do the same with labels and auto-label rules, which match on sender, subject or recipient. See labels vs folders for how to keep the set small.
Testing. Developers use plus addresses to create many test accounts that all land in one inbox: maya+test1@, maya+test2@. Many signup forms treat these as different users, which is exactly what a test needs.
Where plus addressing breaks
Websites that reject the plus sign
Some forms refuse any address with a + in it, because their validation is stricter than the email standard. The plus sign is legal in the local part, so this is a bug in the site, but you still cannot sign up. If it happens, use an alias instead. If you build forms yourself, do not reject the plus sign: signup email validation explains what is safe to check.
Sites that strip the tag
Other sites quietly remove everything after the plus before storing your address. You think you gave them [email protected], but they hold [email protected]. Your tracking is gone and you will not find out until the spam arrives with no tag.
Duplicate account checks
Some services treat [email protected] and [email protected] as the same person, to stop people creating many free trials. If you try to open a second account this way, it may fail with a vague "address already in use" message.
The base address is exposed
Anyone who sees [email protected] can delete the tag and write to [email protected]. A spammer who buys lists with tagged addresses can do exactly that. So plus addressing helps you learn where an address leaked, but it does not protect the mailbox.
Rules can be bypassed
If you filter by tag, the filter only works while the tag stays attached. A sender who removes the tag, or a service that replies from a different system, lands in your inbox with no label.
Where aliases are the better tool
Public and role addresses. Put hello@, support@ or billing@ on your website and in your signature as aliases that point to the right place. You can change who receives them without changing the address people use. Naming team addresses covers which ones a team needs at each stage.
Keeping the real address private. An alias never shows the mailbox behind it. If it starts to attract spam, delete or replace it, and the base mailbox stays untouched.
Moving between people. When a person leaves, the alias stays. You point it to someone else. A plus address tied to one person's name cannot do that. See migrating aliases, groups and shared mailboxes if you are moving a domain.
Sending as the address. If you want to reply from billing@ and not from your personal address, you need an alias (or a shared mailbox) set up for sending. Plus addresses are meant for receiving.
A practical setup
For most small teams, this combination avoids almost every problem:
- One personal address per person, such as
maya@, used for people and accounts that matter. - A handful of role aliases on the domain, such as
support@,billing@andhello@, each pointed at the right mailbox or shared mailbox. - Plus tags for yourself, only on services where you want to track a leak or filter automatically, and only on sites that accept them.
- No catch-all. A wildcard address is not a substitute for planning. Why catch-alls attract spam explains the cost.
Write the list down in a shared document: which aliases exist, who reads each one and what it is for. A list that nobody maintains is how old addresses keep receiving mail that no one reads.
Habits that help
- Use a short, consistent tag style.
+shop-nameis easier to filter than free-form text. Avoid spaces and unusual characters. - Test the address first. Send yourself a message to the tagged address before you give it to a service, and confirm it arrives.
- Keep one untagged address for critical accounts. Banks, domain registrars and your mail provider itself should use the plain address. If a tag is ever rejected or stripped, you do not want a password reset to go missing.
- Review once a year. Delete aliases that no longer have a purpose. Fewer addresses means fewer places for spam to arrive.
- Check spam reports. When a tagged address starts receiving junk, note the tag, stop using that service for anything important and consider changing the address on that account. Spam traps explained covers how addresses end up on lists you never joined.
A note on privacy and honesty
Neither technique is anonymous. Plus addressing exposes the base address, and an alias is still tied to a mailbox that your provider can see. If you need real separation, for example between a work identity and a personal one, use a separate mailbox. Do not use tricks like these to sign up many times for a free trial that is meant to be one per person. Terms of service usually forbid it, and accounts get closed.
Key takeaways
- Plus addressing is quick, free and good for tracking and filtering, but it exposes your base address and some websites reject or strip it.
- Aliases take a minute to set up and are better for anything public, shared or long-lived.
- Keep plain, untagged addresses for critical accounts, avoid catch-alls and write down what each alias is for.
- Use tags for yourself, aliases for everyone else, and a small written list to keep both under control.
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