How to customize unattended-upgrades notification emails?

Question

Is there any way to customize the unattended-upgrades results mail in ubuntu?

The current configuration in /etc/apt/apt.conf.d/50unattended-upgrades file -

// Send email to this address for problems or packages upgrades
// If empty or unset then no email is sent, make sure that you 
// have a working mail setup on your system. The package 'mailx'
// must be installed or anything that provides /usr/bin/mail.
//Unattended-Upgrade::Mail "root@localhost";

sends an email on every run. Instead, I would like to customize it to send only on error. Is there any way I can configure that?

Answer 1

Don't know why they deleted this line on Ubuntu, but Debian includes:

// Set this value to "true" to get emails only on errors. Default
// is to always send a mail if Unattended-Upgrade::Mail is set
//Unattended-Upgrade::MailOnlyOnError "true";

If your /etc/apt/apt.conf.d/50unattended-upgrades don't include the line (and the changelog don't give away this change in presice) is very odd, but at least it doesn't say they changed the behavior. I use a slightly updated version (0.80~sid2 opposed to 0.79.3ubuntu4 that Ubuntu includes in the precise-updates repository) and it will send a mail only on errors (I hasn't get a mail for now). Just write the lines to your configuration file, and everything should be working:

Unattended-Upgrade::Mail "[email protected]";
Unattended-Upgrade::MailOnlyOnError "true";

You may want to run sudo unattended-upgrade -v -d --dry-run to check the entire process yourself.

Answer 2

Works as of Linux Mint 20 which is pretty much Ubuntu 20.04.
To quote the comments in the file

Set this value to one of:
"always", "only-on-error" or "on-change"
If this is not set, then any legacy MailOnlyOnError (boolean) value
is used to chose between "only-on-error" and "on-change"

Unattended-Upgrade::MailReport "only-on-error";