Kit (formerly ConvertKit) is the go-to ESP for independent creators, newsletter operators and course sellers. Its deliverability is generally strong — but shared-IP newsletters are hit every week by something a creator has no control over: a neighbour on the pool sending spammy content, burning the reputation for everyone. The good news is that one specific setting fixes most placement issues, and a free placement test takes three minutes.
Authenticate with a custom sending domain (your own domain, not ckgrid.com). That single change fixes roughly 60% of Kit deliverability complaints. Then test placement per provider before each broadcast — free, no signup, 20+ inboxes.
Kit's sending infrastructure
Kit sends on shared IP pools segmented by plan tier and account reputation. Every account starts on a warming pool for ~30 days before graduating to a normal pool. Creator Pro accounts get access to a higher-tier pool with tighter complaint thresholds, but it is still shared.
The underlying infrastructure is solid — Kit has a dedicated deliverability team and their overall placement numbers compare well to Mailchimp and ActiveCampaign. The problem is that your placement on any given broadcast depends on what the pool's worst sender did in the last 48 hours.
Why Gmail files most Kit broadcasts under Promotions
Gmail's Promotions tab is not a punishment — it is a feature. The classifier looks for:
- Newsletter-style layout (header image, multiple sections, footer links).
- Bulk-sent From address with many recipients from the same domain.
- Unsubscribe footer and marketing-style call-to-action buttons.
- Pool-level signals indicating commercial traffic.
All of those describe a well-formatted Kit broadcast. Landing in Promotions is the default state, not a failure. What you want to avoid is Spam — and Spam placement on Kit traces to three root causes in almost every case.
The "one setting" (custom sending domain + DKIM)
By default, Kit sends from yourname@send.convertkit-mail.com (or the Kit-branded equivalent). The shared sending domain is reasonable but carries all the pool's reputation weight. Switching to a custom sending domain does three things at once:
- DKIM signs under your domain — receivers judge your reputation separately from the generic Kit pool.
- DMARC aligns — the
d=in the DKIM header and the visible From address now share the same organisational domain. Gmail and Yahoo's 2024 bulk-sender rules require this. - SPF alignment via custom return-path — if you also set up a custom return-path, SPF aligns too, and DMARC passes on every send.
Setup takes about 10 minutes: Kit provides a CNAME record to add to your DNS, you verify in their dashboard, done. There is no reason not to do it unless you are on the free plan that does not allow it.
Gmail and Yahoo's 2024 sender requirements enforce DMARC alignment for any sender pushing >5,000 messages per day to their respective user bases. Kit broadcasts often cross that threshold the moment you pass a few hundred subscribers. Custom domain + DKIM is the one-shot fix.
Running a free placement test
Before sending your weekly broadcast to the full list:
- Create a segment in Kit containing only the seed-mailbox addresses from the free placement tool.
- Schedule the broadcast to that segment only, with identical subject line, preheader and HTML.
- Check the placement tool 2–3 minutes later.
- Read per-provider: Gmail Primary vs Promotions vs Spam, Outlook Inbox vs Junk, Yahoo Inbox vs Bulk, plus Fastmail, ProtonMail, Mail.ru, Yandex and others if your audience includes them.
- If any provider shows >10% Spam, pause before sending to the full list. Investigate DMARC alignment and content triggers.
Reading Kit's deliverability dashboard
Kit's broadcast report shows Delivered, Opened, Clicked, Unsubscribed, Complained. Same caveat as every other ESP: Delivered is acceptance by the receiving MTA, not Inbox placement. A broadcast with 97% Delivered and 12% opens is almost certainly a Promotions-tab broadcast — which is not a deliverability problem, just a Gmail-category problem.
Kit does expose Complained as a separate metric. Watch it carefully: anything above 0.1% on a broadcast is a warning sign, and above 0.3% triggers Kit's own internal review. Repeated high-complaint broadcasts can move you to a lower-tier pool.
When Kit's Creator Pro pool actually helps
Creator Pro adds a better shared pool, advanced analytics and the subscriber scoring system. The deliverability benefit is real but modest:
- Tighter complaint thresholds on the pool = fewer bad neighbours.
- Priority sending queue = less batch-variance across large sends.
- Reputation monitoring by the deliverability team.
Creator Pro is worth it if you send to >25k subscribers weekly. Below that, the gap is small enough that the custom sending domain and clean list hygiene matter more than the plan tier.
GlockApps comparison
GlockApps handles Kit broadcasts fine — just forward the broadcast to the seed list. Pricing is the constraint: starter plans start around $59/month for 200 tests, which a creator running a weekly newsletter plus monthly automations will burn through in a quarter. Our free tool does the same 20+ providers including CIS providers, with unlimited tests and no signup.