Check the message
In Gmail: Show original, then copy the HTML part. In your sending tool: the template's source view.
How it works
Measure
The raw message is measured in UTF-8 bytes and compared with Gmail's 102 KB clipping threshold. Readable text is extracted and compared with the total.
Links
Every href and bare URL is listed with its organisational domain, checked for shorteners, plain http, and visible text that names a different domain than the target.
Images
img tags are read for size attributes, hidden styles and tracking-pixel paths. Visible images and pixels are counted separately.
Align
If you enter your sending domain, every link is marked own or external — external click-tracking domains are the usual finding.
The 102 KB clip
Gmail truncates any message larger than 102 KB and shows a "View entire message" link at the cut. The number is bytes of source, not what you see, and inline CSS from a template editor gets there fast. The practical consequence for outbound is that the unsubscribe link and the open-tracking pixel both live at the bottom of the message, so a clipped message reports zero opens and, for bulk mail, fails the unsubscribe requirement. It also looks broken, which is the part the prospect notices.
Links are reputation you borrow
When a filter evaluates a message, every domain in it is checked. A cold email from acme.co with a link to cal.acme.co is one reputation. The same message with click tracking on the sending tool's shared domain is two, and the second one is shared with every other customer of that tool, including the ones who send badly. This is why I set up a custom tracking domain on every fleet before the first send, and why the tool asks for your sending domain — it marks every link that borrows someone else's name.
Pixels and images
An open-tracking pixel is a one-by-one image loaded from a tracking server. Filters recognise the pattern, Apple Mail Privacy Protection loads every pixel whether the mail was read or not, and Gmail proxies images so the number was never accurate anyway. For cold outreach I turn opens off entirely: the signal is worthless and the pixel is one more bulk marker. Visible images are the same argument in a smaller way — a text-only first message from a person does not have a header banner.
Text-to-markup ratio
A personal note is mostly text. A newsletter is mostly HTML. A message that is 90% markup wrapping three sentences was made in a drag-and-drop editor, and filters have seen enough of those to know what they usually contain. If the ratio comes back under 25%, paste the copy into a plain text editor and send that instead; the sending tool will wrap it in the minimum HTML it needs.
Frequently asked questions
Why does Gmail clip my email?
Any message whose HTML source exceeds 102 KB is truncated with a 'View entire message' link. The limit is on source bytes, so inline styling and long tracking URLs count even though they are invisible.
Do tracking pixels hurt deliverability?
They are a recognised bulk-mail pattern and, since Apple Mail Privacy Protection, the open numbers they produce are inflated to the point of uselessness. For cold outreach, turning open tracking off removes a signal and loses nothing.
What is the ideal size for a cold email?
Under 10 KB. A plain-text message with a signature is two or three. If a first-touch message is over 30 KB, something in the template is doing work it does not need to.
Why does the tool care what domain the links use?
Filters evaluate every domain in a message. Links on your own domain share your reputation; links on a sending tool's shared tracking domain share that tool's reputation with all its customers.
Does this send my email anywhere?
No. Parsing happens in your browser. Nothing is uploaded or logged.
Last reviewed
What to run next
The checks that most often follow this one.
More in this category
Guides that go deeper
When the tools tell you something is wrong
The diagnostics here are free and always will be. When the fix is bigger than a DNS record, this is the work I do.
Deliverability rescue
Mail landing in spam, replies gone quiet, or a domain suddenly blocked. I find the actual cause rather than guessing, and fix it.
- Authentication and alignment failures
- Blocklist delistings and reputation repair
- Gateway and filter-level blocks
- A written report on what broke and why
Email & sending infrastructure
Sending domains, inboxes, authentication and warmup, built to survive volume instead of burning down in a month.
- Domain and inbox fleets at any scale
- SPF, DKIM, DMARC and tracking domains
- Google Workspace — Silver Partner
- Handover documentation you actually own
Domain, DNS & migration
Changing registrar, mail provider or host without a day of downtime or a week of mail silently failing.
- Registrar and nameserver moves
- Workspace and Microsoft 365 migrations
- MX, SSL and subdomain cutover
- Staged rollout with rollback at every step
Monitoring & retainer
Infrastructure drifts. Records get edited, certificates expire, domains get listed. Ongoing eyes on the fleet.
- Scheduled checks across every domain
- Alerts before your clients notice
- Monthly reporting
- Priority response when something breaks
Start with a call
Bring a domain and the symptom. I will tell you what is actually wrong and whether you need me at all — plenty of people leave that call able to fix it themselves.
Thirty minutes, no pitch
We will run the checks together on your actual domains, and you will leave knowing what is broken, what it takes to fix, and what it should cost. If that is a job you can do in-house, I will say so.