Regexes in Aliases

How to use regular expressions in your ImprovMX Aliases.

What Are Regex Aliases?

Use regular expressions to match patterns in email aliases and forward them dynamically. This lets you handle multiple similar addresses with a single rule.

A common pattern that you can set up easily:

Using substitutions

You can use $1, $2, etc. to insert values matched by regex groups (parentheses) into the destination email address.

  • $1 = first matched group, $2 = second group, and so on.
  • This allows you to dynamically forward emails based on parts of the alias.
Example:

Let's say you have an alias defined as:

If someone sends an email to: john.doe@yourdomain.com‍

Result: The email forwards to: john.doe+john@gmail.com

Note: The alias field must not exceed 150 characters

Order of importance when matching an email

We evaluate alias matches in the following order of importance:

  1. The exact match
  2. The “Plus sign” match
  3. The Regex match
  4. The Wildcard or catch-all match *

Regardless of how many aliases an email matches, only the highest priority rule activates.

Example:

Given these aliases:

Even though contact@... matches multiple rules, the exact match i.e. "richard.hendricks@gmail.com" takes priority.

Example email matches based on the above configuration:

  • contact@piedpiper.com → richard.hendricks@gmail.com – Exact match
  • support@piedpiper.com → dinesh.chugtai+support@gmail.com – Regex match
  • postmaster@piedpiper.com → gilfoyle+wildcard@gmail.com – Wildcard match
  • contact+jared@piedpiper.com → richard.hendricks+jared@gmail.com – Plus sign match

    • The “plus sign” match

    When an email is sent to an address with a plus sign (e.g., contact+label@piedpiper.com), ImprovMX:

    • ‍Matches it to the base alias (e.g., contact@piedpiper.com)‍
    • Forwards to the configured destination (e.g., richard.hendricks@gmail.com)‍
    • If the destination is a Gmail address, ImprovMX adds the same +label to the Gmail address
    Example

    Let's say you have the below forwarding setup:

    Actual Email sent to: contact+newsletter@piedpiper.com

    Final forwarded to: richard.hendricks+newsletter@gmail.com

    ImprovMX strips the +newsletter when matching the alias, but re-applies it to the Gmail destination for consistency.

    Note: Only works for @gmail.com and other domains below, not for G-Suite domains.

    List of accepted domains for Regex plus sign forwarding

    • gmail.com
    • hey.com
    • protonmail.com
    • icloud.com
    • fastmail.com
    • outlook.com
    • runbox.com
    • yandex.com
    • yandex.ru
    • mailfence.com

    If you have any questions about regex forwarding, feel free to contact us.

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