Mailcamp lets you create email content with the builder, edit HTML directly, or upload your own template package. File limits exist to keep the editor stable, prevent oversized email content, and reduce deliverability problems caused by heavy templates.
The exact upload size can depend on your plan and server configuration. When Mailcamp shows a maximum upload size message, use that value as the current limit for your account or environment.
Template upload: when you upload your own email template package.
Builder image upload: when you add or replace images inside the email builder.
Template assets: when a template package includes images, CSS, or other supporting files.
Server upload limit: when the uploaded file is larger than the maximum file size allowed by the server.
Upload templates as a .zip file.
The ZIP package should include the main HTML file and any required assets.
Keep the template structure simple so Mailcamp can read and store the content correctly.
Avoid unnecessary files, design exports, screenshots, or large source files inside the ZIP package.
If the upload fails, check whether the ZIP file is valid and below the maximum upload size shown by Mailcamp.
Images uploaded in the builder must be valid image files.
Supported image formats include JPEG, JPG, PNG, GIF, BMP, and WebP.
The builder checks the file size against the server upload limit before uploading.
If an image is too large, Mailcamp may show a message such as File too large.
Compress large images before uploading them to keep the email fast and lightweight.
Large HTML files can make the editor slower to load and save.
Large images can make emails load slowly for subscribers.
Heavy emails can be clipped or partially hidden by some inbox providers.
Oversized templates can increase the chance of rendering issues across email clients.
Large or messy code can make spam filters more cautious, especially when combined with poor sender reputation.
Resize images to the display size needed in the email before uploading.
Compress images using an image optimization tool.
Remove unused CSS, comments, tracking scripts, and code generated by page builders.
Host very large files on your website and link to them instead of embedding them in the email.
Use web-safe layouts and email-friendly HTML instead of complex website-style HTML.
Keep the email focused on the message, with a clear link to a landing page or website for heavier content.
Use email-specific HTML templates, not full website pages.
Test the template after uploading it to make sure images, buttons, and links still work.
Add the required unsubscribe link before using the template in a marketing campaign.
Preview the email on desktop and mobile before sending.
Send a test email to check how the template renders in a real inbox.
The ZIP upload fails: confirm that the file is a valid ZIP package and below the maximum upload size.
The builder rejects an image: check that the file is a supported image type and not larger than the allowed upload size.
The template loads slowly: reduce image sizes and remove unnecessary HTML or CSS.
Images do not appear after upload: check that the image files are included in the template package or upload them again through the builder.
The email is clipped in an inbox: simplify the HTML and reduce the total size of the email content.
The campaign cannot be saved: make sure the email contains the required unsubscribe link for marketing campaigns.