Postfix SMTP client whitelisting

I run a Postfix + Dovecot email server for my personal email. Common setups include reject_unknown_reverse_client_hostname for SMTP clients to reduce invalid connections attempts, but this became a problem when my new metro wireless ISP assigned me an IP that has no PTR record, causing my mail server to reject my own local email client’s SMTP connections!

In this post I present two solutions: simply adding permit_sasl_authenticated to the SMTP client restrictions, or implementing a more complex but generic whitelist via check_client_access and a MariaDB (or MySQL) database table.

Migrating Signal to a new Note 8

I recently purchased a Galaxy Note 8 to replace my aging Note II, and am in the process of migrating data. Most items are relatively trivial to move over, but Signal Private Messenger tries to be secure enough that it ends up being impossible to migrate non-text content with standard methods – images, voice, and group chats are not transferred.

After some investigation and several ADB versioning issues, I have successfully tested a workaround for migrating Signal data between Android devices.

Setting up OpenVPN with Android and Tomato

I recently updated my router’s firmware to Advanced Tomato, which is just a modern HTML5 reskin of Tomato by Shibby, which is an update of the original Tomato for the famous WRT54GL. Tomato is a router firmware that supports a wide variety of improved functions, including QoS, realtime bandwidth monitoring and logging, easy LAN DHCP management, etc. – including an OpenVPN server and client, as well as a few other VPN solutions. Tomato supports a number of routers, including my ASUS RT-N16.