Emails: Add Expires header

[rickbutterfield]

Prerequisites

• I have added steps to test this contribution in the description below

Description

As part of discussions with the Sustainability team, we are proposing adding the ability to add the standardised Expires: header to emails sent from the EmailSender. Based on ideas proposed by the Email Expiration Date initiative, a growing number of providers are beginning to support the standard and will delete emails at the specified expiry date, reducing the number stored over long periods of time contributing to higher carbon emissions.

This value is set as a TimeSpan and is configurable at a global level in appsettings.json. There is no default value as we would prefer it to be opt-in currently.

A value can also be specified when using IEmailSender through dependency injection, meaning that other packages and extensions sending emails can take advantage of this and allow expiration dates to be set.

Some emails sent from Umbraco now have an Expires value set:

• 1 hour for password reset (based on information I could find about ASP.NET Identity TokenLifetime)
• 72 hours for backoffice invites (based on text shown in the backoffice when inviting a new user)

When testing this, confirm by checking email headers that:

1. An Expires header is present
2. The header is the right amount of time ahead of when it was originally sent
3. The date is in the correct format

References:

• https://www.zerocarbon.email/documentation/define-expiration-times-emails/
• https://www.ietf.org/archive/id/draft-billon-expires-08.html

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Pull Request Overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[AndyButland]

Had a few thoughts on this one @rickbutterfield - please see the inline comments and let me know what you think.

[Copilot]

Pull Request Overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

src/Umbraco.Core/Configuration/Models/SecuritySettings.cs:1

• The UserInviteEmailExpiry property is incorrectly initialized with StaticPasswordResetEmailExpiry instead of StaticUserInviteEmailExpiry. This will cause user invite emails to expire after 1 hour instead of the intended 72 hours.

// Copyright (c) Umbraco.

[AndyButland]

I've tested this out and verified that the expected headers are included in the email messages. All looks to work as expected, nice work @rickbutterfield.

I pushed a couple of changes to resolve further breaking changes on the interface, and also to simplify the interfaces a bit. I felt we didn't really need all the overloads, so have reduced to one method with the others obsoleted. But would appreciate your view on that.

Please let me know if you are happy with this, and if so, will merge in.

We'll need to document these additional options, which I'll prepare a PR for,

[AndyButland]

Docs PR is here: umbraco/UmbracoDocs#7482

[rickbutterfield]

This all looks great @AndyButland, and thank you for sorting a docs PR too! H5YR!