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Disposable E-Mail Addresses with Postfix

The digital nomad needs three things - a professional e-mail address, a private e-mail address and an unlimited number of disposable e-mail addresses. The usefulness of the priv/pro combo of addresses is quite obvious and shall not be discussed here.

For what do we need disposable e-mail addresses?

Some years ago, I registered myself to the Adobe Forums and for various reasons, I did not like so much the idea of utilizing one of my real e-mail addresses for validating the registration. Instead, I informed an e-mail address in my mail domain example.com, but with the local part changed to adobe. I only needed to make sure that e-mails to adobe@example.com were redirected to my personalized address. Then, in November 2012, Adobe was hacked, and the user database with about 150,000 entries was stolen by a hacker who named himself „VirusS_HimA“.

Apparently VirusS_HimA sold the thus obtained e-mail addresses to the spammers of the world, and even in 2018 adobe@example.com is addressed by a handful of spam attempts every day, which of course are blocked by my Postfix mail server in the RCPT TO: phase of the SMTP protocol.

File /usr/local/etc/postfix/invalid_recipients:

adobe@example.com      REJECT
...

File /usr/local/etc/postfix/main.cf:

...
smtpd_recipient_restrictions = permit_mynetworks,
                               permit_sasl_authenticated,
                               check_policy_service unix:private/greyfix,
                               check_recipient_access hash:/usr/local/etc/postfix/invalid_recipients,
                               permit
...

Needless to say, that adobe@example.com cannot be used anymore for any other purposes than not receiving spam, and the respective account in said forums has been orphaned, of course. Effectively, said address has been disposed off, and this example shows quite nicely the usefulness of disposable e-mail addresses.

I used in the past a lot of disposable addresses, some of which are still in use, and others were already disposed off in the same manner as the adobe one. In effect, my personalized priv/pro e-mail addresses are kept clean from all this nonsense, call it black spam or white mail noise. Nowadays, every idiot sends you every three month an update to his privacy declaration and expects you to read and confirm 10 pages of pure bull shit, and here, this ends-up directly where it belongs to anyway, in the data sewer.

The missing piece

In order to easily receive e-mails to your disposable e-mail addresses, it is best to configure a catch-all user in your mail domain. This needs to be done only once, and with this in place you could inform disposable addresses on the fly at any time when needed and without any server-site reconfiguration.

File /usr/local/etc/postfix/catchall_recipients.pcre:

# PERSONALIZED CATCHALL
/^.*me@example\.com$/ me@example.com
/^.*he@example\.com$/ he@example.com
...
# GENERAL CATCHALL
/^.+@example\.com$/   me@example.com

File /usr/local/etc/postfix/main.cf:

...
local_recipient_maps                = $alias_maps,
                                      hash:/usr/local/etc/postfix/smtp_local_recipients
virtual_alias_maps                  = pcre:/usr/local/etc/postfix/catchall_recipients.pcre
unknown_local_recipient_reject_code = 550
...

Copyright © Dr. Rolf Jansen - 2018-05-29 20:53:05

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