Is it OK to put a customer's name or email address in a UTM link so I know who opened my message?
No. The customer sees the link, and so does anyone they forward it to, and UTM values are kept in your analytics reports with every visit. Many analytics providers also forbid sending personal information to them in their terms, so check your provider's. Use UTM values to describe the campaign, the placement and the audience group, never people.
Why the idea is tempting, and why it is wrong
You have a list of two hundred customers and want to know who clicked the Eid offer. The obvious shortcut is one link per customer with their email in the content field. But that link does not stay between you and the customer. It shows in their address bar, lands in their browser history, and if they forward it to a friend or post it in a group, their email goes along to everyone who sees it.
Then the value reaches your analytics tool and is stored in its reports, visible to everyone with access to your account, possibly for a long time. You never asked the customer's permission, and they have no idea it is happening.
Encoding hides nothing
You might think the link turns the email into unreadable codes. We put a test address in the content field of the UTM campaign link builder, and this is what came out:
https://example.com/eid?utm_source=newsletter&utm_medium=email&utm_campaign=eid_2026&utm_content=sara%40example.com
The @ became %40 and nothing else changed; the address reads as plainly as before. Encoding makes the link technically valid; it protects nothing. Anyone can decode it in a second with a tool like the URL encoder/decoder.
What to use instead
Split the list into groups that mean something to you and give each group a descriptive value. The same link for your top customers:
https://example.com/eid?utm_source=newsletter&utm_medium=email&utm_campaign=eid_2026&utm_content=vip_list
- Groups by behaviour: vip_list, new_customers or inactive_90d.
- Groups by city when the offer is local: riyadh or dubai.
- The message version if you are testing two subject lines: subject_a and subject_b.
These values answer the question that actually helps your shop, which group responds to which offer, without exposing anyone.
What if you really need to know who opened the message?
That is a job for the email tool you send with. Many show per-subscriber open and click reports inside your account, without putting anything in a public link, and what they show is covered by the privacy terms the subscriber agreed to. UTM tags are for campaigns, not individuals.
The tool builds the link inside your browser and sends it nowhere, but it cannot stop you typing personal information into a field. That decision is yours before you copy.
Common questions
What about an order number or customer number?
Same rule: any number that points to one specific person does not belong in a link that gets published or sent. Use values that describe the group.
Is an influencer's name in the source personal data?
The public account name of someone you work with describes a marketing channel, which is different from customer data. Still, use the agreed account handle rather than their full name.