Email subaddressing

What is subaddressing?

Subaddressing allows delivery to multiple email addresses by using a single mailbox on our servers when certain conditions are met. The local part of a mailbox name (the part before the @ symbol in the address) on our servers can be split into a prefix and a tag with the "-" (minus) symbol. The part before the minus is called a prefix, while the part after the minus is called a tag. The prefix@ mailbox needs to be an actual mailbox on the account in order for subaddressing to work. The prefix-tag@ combination, where the tag part can be any string, acts as an alias for the prefix@ mailbox. We refer to this convention as subaddressing, but it is also known as tagged addressing, or mail extensions (and sometimes plus addressing, although the minus is used here).

How to manage the subaddressing option for a mailbox?

The subaddressing option for a particular mailbox can be enabled or disabled through the "Filters" page of the mailbox. This page can be accessed by clicking on the "Filters" button next to the mailbox name in the Mail Manager in the Control Panel of the hosting account:

There, look for the Subaddressing section. To enable or disable the option, click on the button in this section:

You can also enable or disable subaddressing while creating email accounts by selecting the appropriate option. The default new mailbox setting follows the global configuration on your account.

How to manage the subaddressing option for all mailboxes?

You can enable and disable subaddressing for all mailboxes on the account through the "Global mail settings" tab in the Mail Manager in the Control Panel of the hosting account:

There, look for the Subaddressing section. To enable or disable the option, click on the button in this section:

Please note that enabling or disabling subaddressing for all mailboxes on the account will overwrite any individual mailbox setting.

Special conditions

The server will interpret everything after a minus as a tag. However, there might be an actual mailbox on the account that has a minus in its name, and the part before the minus in this mailbox name matches the prefix of a mailbox that has subaddressing enabled. In this case, the server will deliver a message sent to the mailbox that has a minus in its name to the actual mailbox.

Since the server treats everything after a minus sign as a tag, if a mailbox name includes a minus and its first part matches another mailbox with subaddressing enabled, this can affect message delivery:

• If an email is sent to a mailbox with a minus in its name (e.g., firstname-lastname@), it will go to that exact mailbox.
• If an email is sent to firstname-lastname@ with an extra tag (e.g., firstname-lastname-substring@), the server will deliver the message to firstname@ instead. The firstname@ must exist and subaddressing should be enabled for either mailbox.
• If a firstname@  mailbox does not exist, and an email is sent to firstname-lastname@ with an extra tag (e.g., firstname-lastname-substring@), the server will bounce the message, even if subaddressing is enabled for firstname-lastname@.

Example:

• firstname-lastname@ exists and allows subaddressing.
• firstname@ also exists.
• An email to firstname-lastname-extra@ will go to firstname@, not firstname-lastname@.
• This happens because the server always treats everything before the first minus as the prefix of the intended mailbox name when subaddressing is active.