Email deliverability checklist: 15 checks before your next campaign

Getting an email accepted by a mail server doesn’t guarantee anyone will see it. A campaign can technically be delivered and still land in spam, get filtered away from the primary inbox or struggle because the sending domain has picked up a poor reputation.

Deliverability problems are easier to fix when you stop treating them as one big mystery. Most issues can be traced back to a smaller set of checks around authentication, list quality, sending behavior and what happens after the send.

Use this checklist before an important campaign, or work through it when performance suddenly drops.

TL;DR: A strong email deliverability checklist should cover SPF, DKIM and DMARC, sender reputation, list hygiene, complaint rates, unsubscribe setup, sending patterns, content, bounce handling and post-send monitoring.

Email deliverability checklist: what to review

1. Authenticate your sending domain

Start here before changing subject lines or rewriting copy.

Email providers use authentication to verify whether a message is genuinely allowed to come from your domain.

For Gmail, all senders need SPF or DKIM. Senders exceeding 5,000 messages per day to Gmail accounts need SPF, DKIM and DMARC. Google also requires the From domain to align with either SPF or DKIM for bulk sending. 

In Transpond, domain authentication is configured under Account Settings → My Domains. The platform provides the SPF and DKIM records to add to your DNS.

Check

• SPF exists and includes every legitimate sender
• DKIM is enabled for the sending domain
• DMARC is published
• The From domain aligns correctly

One small but important detail: if your domain already has an SPF record, don’t add another one. Transpond recommends editing the existing record and adding its include value there. Multiple SPF records can break authentication. 

2. Check DMARC alignment, not only whether DMARC exists

A DMARC record sitting in DNS doesn’t automatically mean messages are aligned correctly.

For direct mail to Gmail, the organizational domain in the visible From header needs to align with either the SPF domain or DKIM domain. Google currently requires bulk senders to have both SPF and DKIM configured, although only one needs to align for DMARC.

This needs closer attention when email is being sent through several different systems. Your newsletter platform may authenticate correctly while a CRM, support system or transactional service uses a different setup. An email deliverability audit should look at the whole sending ecosystem, not just the marketing tool.

3. Make unsubscribing easy

A subscriber who can’t leave cleanly has another option: mark the message as spam.

If you send marketing or subscription emails in bulk, Gmail expects recipients to be able to unsubscribe in one click and find an unsubscribe link within the message.

Check the experience:

• Send yourself a live campaign email. Use the same template, sender, and sending setup your subscribers receive. A test from the editor may not behave exactly like the real campaign.
• Click the unsubscribe link yourself. Check where it leads and whether the page loads properly on both desktop and mobile.
• Complete the full unsubscribe flow. The subscriber shouldn’t need to log in, create an account, or fill out unnecessary fields just to leave the list.
• Count how many steps it takes. One click or one simple confirmation is usually enough. If people have to work through several screens, the flow is creating avoidable friction.
• Check the contact record afterward. Confirm the address is marked as unsubscribed or suppressed in the platform, rather than relying on the confirmation page alone.
• Try sending another marketing email to the same address. The platform should prevent the send or exclude the contact automatically.
• Read the confirmation page like a subscriber. It should clearly explain that the request was successful. Avoid vague wording that leaves people unsure whether they are still subscribed.
• Repeat the test across every platform sending email for the brand. Suppression rules can differ between tools, so a working unsubscribe flow in one system doesn’t guarantee the same result everywhere.

The easier it is to unsubscribe, the less reason someone has to complain instead.

4. Watch your spam complaint rate

Google tells senders to keep spam rates reported in Postmaster Tools below 0.3%. Treat 0.3% as a ceiling, not a target.

If complaints start climbing, look at which campaigns caused them. A sudden jump after one send points to a different problem than a steady increase over several weeks.

Questions worth checking include:

• Did you send your email campaign to an older segment?

• Was the campaign expected by the recipients?

• Did frequency increase recently?

• Was the sender name different?

• Did the audience come from a new source?

Complaint data is more actionable when you connect it to a specific change in sending behavior.

5. Remove addresses that shouldn’t be mailed

A growing list can still become less deliverable if stale and invalid addresses keep accumulating. Some addresses go stale over time, while others belong to people who stopped engaging long ago or barely remember signing up in the first place.

Review:

• hard bounces
• repeated soft bounces
• unsubscribed contacts
• obviously invalid addresses
• old contacts with no meaningful engagement

Transpond includes list cleaning functionality designed to filter invalid or unused addresses before they become a recurring sending problem.

For imported lists, spend extra time here. A clean-looking CSV can still contain contacts collected years ago or addresses that were never meant for marketing.

6. Don’t treat every inactive subscriber the same

No opens lately? Don’t suppress the address just yet.

Open-rate data isn’t reliable enough on its own. Before deciding what to do with an inactive contact, check:

• Have they clicked anything recently? A click is a much stronger sign of interest than an open.
• Have they purchased, submitted a form, or visited the site? Recent activity outside the inbox may show the relationship is still active.
• Were they engaged in the past? A long-time customer who has gone quiet deserves different treatment from an address that has never interacted.
• How long have they actually been inactive? Define a window that makes sense for your sending frequency. Six months means something very different for a weekly newsletter than for a quarterly campaign.

Still seeing signs of interest? Keep the contact and adjust the messaging or frequency.

No meaningful activity anywhere? Run a re-engagement campaign before suppressing them. Give the subscriber a clear reason to stay and an equally clear way to leave.

If there’s still no response, stop sending regular campaigns. Keeping silent contacts indefinitely adds volume to the list, but not value.

7. Check for sudden sending-volume changes

Mailbox providers learn from sending patterns. A domain that normally sends 5,000 emails a week and suddenly pushes 100,000 has changed its behavior dramatically.

The volume itself isn’t automatically wrong, but the change deserves scrutiny.

Large list imports, seasonal campaigns and business growth can all increase sending volume legitimately. In those cases, ramping up gradually gives the sending domain a more consistent pattern than moving from very little traffic to maximum volume overnight.

This is especially relevant for new domains.

8. Check where your contacts came from

Deliverability begins before the first email is written.

A list built from people who knowingly subscribed behaves very differently from a database assembled through third-party sources.

Before sending to a new segment, ask:

How did these people get onto the list?

If nobody can answer clearly, don’t send just because the addresses exist.

Purchased lists are especially risky because consent, list age and previous sending history are often unknown.

9. Check your From name and From address

Recipients should immediately recognize who is contacting them. The sender name and address should feel familiar, match the brand, and stay consistent across campaigns.

Do

• Use a recognizable sender name. If subscribers know the brand as Transpond, keep Transpond visible in the From field.
• Send from a branded domain. An address such as hello@transpond.io is clearer than an unrelated or generic domain.
• Keep the setup consistent. Frequent changes to the sender name or address can make legitimate campaigns look unfamiliar.
• Match the visible sender with the technical setup. Your From domain should align properly with authentication and sending infrastructure.
• Test what recipients actually see. Check the sender line in Gmail, Outlook, Apple Mail, and on mobile before sending at scale.

Don’t

• Don’t disguise who is sending the email. Avoid vague names or wording that makes the message look like it came from another company.
• Don’t imitate another organization. Google explicitly prohibits Gmail From-header impersonation.
• Don’t switch sender identities without a reason. For example, moving from Transpond hello@ transpond.io to an unfamiliar name or address can create confusion even when the campaign is technically valid.
• Don’t rely on the address alone. Many recipients notice the display name first, so both elements need to make sense together.

10. Review links before sending

Links deserve a quick QA pass before every campaign.

Start with a test send and click the main CTAs yourself. Make sure each link lands on the page you expect, tracking redirects resolve correctly, and older templates haven’t carried over outdated URLs.

Pay attention to domain consistency too. A campaign packed with links pointing across several unrelated domains can look messy and may create unnecessary trust issues. You should keep only the destinations that serve a clear purpose.

You don’t need to remove useful links or simplify every email into plain text. The aim is much simpler: catch broken paths, unnecessary redirects, and questionable destinations before subscribers do.

11. Test the email before the real send

A preview inside an editor won’t tell you everything.

Before the full send, run at least these three checks:

• Send to several real inboxes. Test Gmail, Outlook, Apple Mail, and any other providers that make up a meaningful share of your audience. Check layout, sender details, images, and CTAs on both desktop and mobile.
• Inspect the journey, not just the email. Click through the main links, watch for unexpected redirects, and confirm that landing pages open correctly with tracking parameters attached.
• Run an inbox-placement test. For larger campaigns, check whether the message reaches the inbox, Promotions tab, or spam folder across different providers. One successful test to your own Gmail account is not enough evidence.

Transpond’s Campaign Wizard includes pre-send checks, including inbox-placement testing, so problems can be caught before the campaign reaches the full audience.

12. Keep frequency consistent with what people signed up for

A lot of deliverability trouble starts with sending habits, not technical setup. If someone signed up expecting one newsletter a month, a sudden jump to daily emails can feel intrusive and quickly change how they react to the brand.

You see this most clearly during periods when send volume increases fast.

Example: a retailer usually sends two campaigns a month, then plans a much heavier Black Friday schedule. Instead of sending every message to the full database, the most engaged subscribers could receive the full sequence. Quieter contacts might only get one or two key offers.

You still increase campaign activity, but without forcing the same frequency on everyone.

13. Don’t diagnose deliverability from open rate alone

Open rate can tell you something changed, but it can’t tell you why.

A fall in opens could come from inbox placement, audience quality, subject lines, seasonality or privacy-related measurement changes.

Look at several signals together:

• delivery and bounce rates
• spam complaints
• clicks
• unsubscribe rate
• performance by mailbox provider

If Gmail performance drops while Outlook remains stable, investigate Gmail-specific reputation or authentication before rewriting the whole campaign.

14. Use Google Postmaster Tools if Gmail is important to your list

Google Postmaster Tools is Google’s own monitoring dashboard for senders. It shows how Gmail sees traffic coming from your domain, including spam complaints, domain and IP reputation, authentication performance, and delivery errors. Google also provides a Compliance Status dashboard that checks key sender requirements.

If Gmail represents a meaningful share of your audience, this is one of the few places where you can see signals directly from Google.

Pay closest attention to:

• Spam rate. A sudden increase deserves investigation, even if opens and clicks still look normal. Google recommends keeping user-reported spam as low as possible.
• Domain reputation. Watch the direction over time. A drop can indicate that Gmail is losing confidence in traffic from the domain.
• Authentication. Check whether SPF, DKIM, and DMARC are passing consistently. A partial setup is not the same as reliable authentication across your actual sending traffic.
• Delivery errors. Rejections and temporary failures can reveal problems before they become obvious in campaign reporting.
• Compliance status. Don’t ignore a Needs work flag. The dashboard covers requirements such as SPF/DKIM, spam rate, DNS and message formatting, with additional checks such as DMARC and one-click unsubscribe for bulk senders.

Also, don’t panic over one strange day. Postmaster Tools data isn’t real time, lower-volume days may show incomplete data, and changes may take time to appear. The value comes from checking it regularly enough to recognize your normal baseline and spot a genuine change.

15. Investigate sudden drops before changing everything

If deliverability drops sharply, start with the timeline. Look at what changed just before the decline: a new sending domain, a large list import, higher volume, authentication changes, or a different audience segment.

Try not to change several things at once. If you rewrite the content, switch infrastructure, and suppress half the list on the same day, you may improve performance without ever knowing what really fixed it.

A simple investigation can look like this:

Performance drops → check whether the issue is limited to one mailbox provider → review authentication and recent setup changes → compare recent audience or list changes → inspect complaints, bounces, and other warning signals → check whether sending volume or frequency changed → test the next campaign on a controlled segment

You should isolate the cause before making broader changes.

Transpond vs other white-label marketing platforms

White-label marketing platforms take different approaches, so the right option depends on the services your agency provides and how much of your workflow you want the platform to handle.

HighLevel combines CRM, funnels, automation, client accounts and other marketing functions in one system. Vendasta takes a marketplace-led approach, with a broad range of products and services agencies can resell. DashClicks combines software with fulfilment, reporting and operational support.

Transpond takes a more focused approach to email marketing, giving agencies tools for campaigns, automations and ongoing client communications under their own brand. This can suit agencies that already have their CRM, project management and other business systems in place and want to add or expand email marketing without replacing their existing setup.

The key consideration is how closely each platform fits the service you want to deliver. A broader platform may make sense if you want to consolidate more of your agency's operations, while a specialist email platform may be a better fit if email is a core part of your client offering.

Bring white-label email marketing to your agency

The best white-label platform is one that supports the services you already sell—or want to add—without creating unnecessary complexity for your team or clients.

If email campaigns, automation and ongoing client communications are part of your offering, Transpond provides the infrastructure to deliver those services under your own brand.

Get started with Transpond and explore how you can offer white-label email marketing to your clients.