Sending an image in an email sounds simple — but the rules are different for every client. Gmail clips emails with too much HTML. Outlook blocks external images by default. Mailchimp has its own image hosting with width constraints. Get any of these wrong and your image either won't display, will be clipped, or worse, will push your email into spam.
This guide walks through the complete workflow: identify your email type, resize to the right width, compress images for email to the correct file size, and deliver in the format each client expects. Five steps, with ready-to-use settings for every scenario.
Pre-Flight: Know Your Email Type Before Touching the Image
Before compressing anything, identify which of these three scenarios applies:
| Email Type | Client | Image Delivery Method | Key Limit |
|---|---|---|---|
| Newsletter campaign | Mailchimp, Klaviyo, ConvertKit | Externally hosted, inserted via image block | 600px wide max, 1MB per image |
| Personal/business email | Gmail, Outlook, Apple Mail | Inline (embedded) or attachment | Gmail total: 102KB HTML; Outlook: 25MB attachment |
| Transactional email | SendGrid, Mailgun, SES | Hosted image URL in HTML template | Deliverability ratio: keep images minimal |
The workflow differs significantly per type. Each step below flags where the path diverges.
The 5-Step Workflow
1 Identify your email type and target client
Confirm whether this is a newsletter, personal email, or transactional message. Your compression target depends on this. Newsletter images in Mailchimp are hosted on Mailchimp's CDN — the recipient loads them from an external URL. Gmail inline images are embedded in the email itself — they count toward the 102KB HTML clipping threshold.
2 Resize to the correct width for your client
Open ConvertiImage and upload your image. Set the resize width based on your email client:
- Mailchimp / newsletter: 600px wide — this is the standard one-column email template width. Images wider than 600px will be scaled down by the email client, sometimes with quality loss.
- Gmail inline: 600–800px wide — any wider and Gmail may display a horizontal scroll bar on mobile.
- Outlook inline: 600px wide maximum — Outlook has inconsistent rendering above this width, especially in older versions.
- Email attachment: No width restriction applies — resize for the recipient's intended use (print, presentation, etc.).
Always resize proportionally — maintain the original aspect ratio. Do not stretch or distort.
3 Convert to JPEG format
This step is non-negotiable for compatibility. Select JPEG as the output format in ConvertiImage before compressing. Here's why each other format fails:
- WebP: Not supported in Outlook (any version). Displays as a broken image or attachment instead of inline image.
- PNG: Supported everywhere but produces larger files than JPEG at equivalent visual quality for photographic content. Use PNG only if the image has transparency (logos, icons).
- AVIF / HEIC: Not supported in any major email client.
- GIF: Acceptable for simple animations in newsletters; Outlook renders only the first frame.
For any photographic image — product photos, banner images, header graphics, portfolio shots — JPEG is the only reliable format for all email clients.
4 Compress to the target file size
Set the JPEG quality slider in ConvertiImage based on the email type:
| Email Type | JPEG Quality | Target File Size | Reason |
|---|---|---|---|
| Newsletter header image | 72–78% | 50–100KB | Loaded from CDN — fast delivery needed for mobile users |
| Newsletter body image | 75–80% | 80–150KB | Multiple images per email — keep each small |
| Gmail inline image | 78–82% | 100–300KB | Gmail clips at 102KB of total HTML — images add to this |
| Outlook inline image | 80–85% | 150–400KB | Outlook renders inline images but recipients may have images blocked by default |
| Portfolio / attachment | 88–92% | 300KB–1MB | Recipient opens separately — quality matters more than delivery weight |
After setting quality, download the compressed JPEG. Check the file size before sending.
5 Deliver using the correct method for your client
Mailchimp: In your campaign editor, click the image block. Click "Upload" and select your compressed JPEG. Mailchimp hosts the image on its CDN and inserts an <img> tag pointing to the hosted URL. Your compressed file size directly determines how fast the image loads for recipients.
Gmail: In the compose window, click the image icon (bottom toolbar). Select "Upload from computer" and choose your compressed JPEG. The image embeds inline. Alternatively, insert it as an attachment if it's a deliverable the recipient needs to download.
Outlook: In the compose window, go to Insert → Pictures → This Device. Select your compressed JPEG. Outlook embeds it inline, but recipients who have "Block images from external senders" enabled will see a placeholder. For important images, add alt text so the message is still readable without the image.
Ready-to-Use Recipe Cards
Copy these settings directly into ConvertiImage for each email scenario.
Newsletter Header Image (Mailchimp / Klaviyo)
This is the large banner image at the top of your newsletter. At 600px wide and 75% quality, a typical header image should compress to 60–90KB — well within what loads instantly on mobile. Always include your brand or campaign message as text in the email, not embedded in the image, so it's visible even when images are blocked.
Newsletter Product Image (E-Commerce Campaign)
Product images in newsletters need enough quality to show detail (color accuracy, texture) without bloating the total email size. At 560px (slightly narrower than the template to allow padding), 80% JPEG gives excellent product rendering at a deliverable size. For product grids (3 products per row), use 180px wide per image at 80%.
Gmail Inline Image (Personal / Business Email)
For images you paste directly into a Gmail body, 700px wide at 82% is the sweet spot. The image displays well on desktop and scales down on mobile. Keep total email HTML under 102KB to avoid Gmail clipping — a single inline image shouldn't exceed 400KB. If you have multiple inline images, use 78–80% quality to keep each one smaller.
Portfolio or Work Sample Attachment (Gmail / Outlook)
When the recipient needs to view or print the image (design deliverable, real estate photo, CV headshot), compress for quality rather than delivery weight. At 1200px wide and 90% JPEG, a typical full-color photo compresses to 400KB–1.5MB — visible in full quality when the recipient opens the attachment, while still well below Gmail's 25MB attachment limit.
Transactional Email Product Thumbnail (Order Confirmation)
Order confirmation emails, shipping notifications, and receipt emails should be as lightweight as possible — these are high-volume, time-sensitive messages where deliverability is paramount. Keep product thumbnails at 200px wide and 78% quality. The total transactional email HTML including all images should stay under 100KB for best inbox placement rates.
Troubleshooting Email Image Problems
| Problem | Cause | Fix |
|---|---|---|
| Gmail shows "Message clipped" link at bottom | Total email HTML exceeds 102KB | Compress all inline images further (target 72% quality), reduce image count per email, or host images externally |
| Images not displaying in Outlook | Recipient has image blocking enabled, or image is WebP/AVIF | Convert to JPEG; add descriptive alt text; encourage recipient to click "Download Pictures" |
| Image looks pixelated in Mailchimp preview | Image uploaded below 600px wide | Always upload at exactly 600px wide — never below. Mailchimp will not upscale. |
| Email going to spam with images | Too high image-to-text ratio, or large total email size | Aim for 60% text / 40% image ratio; ensure every image has alt text; compress all images to reduce total weight |
| Image appears stretched or distorted in Outlook | Explicit width/height HTML attributes conflicting with actual image dimensions | Remove manual width/height HTML attributes from the img tag; let the image render at its natural dimensions |
- Best Way to Compress Images for Email: Reduce Size Without Breaking Rendering (2026) — the full guide with tool comparisons
- Why Large Images in Emails Get Blocked, Clipped, or Sent to Spam (2026) — understand the failure modes
- Best Tools to Compress Images for Email and Newsletters (2026) — tool comparison across 6 options
Frequently Asked Questions
Gmail allows email attachments up to 25MB total. However, for inline images embedded in the email body, the practical limit is much smaller — Gmail clips the entire email if the total HTML size exceeds approximately 102KB. For inline images, keep each one under 400KB and aim for the total email (HTML + inline images) to stay under 100KB. If you have multiple large images, host them externally on a CDN and reference them via URL rather than embedding inline.
No — WebP is not supported in Outlook (any version) and has inconsistent support in older versions of Gmail and Apple Mail. If you send a WebP image, Outlook recipients will see either a broken image placeholder or be prompted to download the file rather than seeing it inline. Always reduce image size for email by converting to JPEG first, then compressing. JPEG has 100% compatibility across all email clients in 2026.
Blurry images in Mailchimp are almost always caused by uploading an image that is too small in pixel dimensions. Mailchimp displays images at the width of your template (typically 600px) but does NOT upscale small images to fill that width — it displays them at their actual size, or the email client scales them up poorly. Always upload images at exactly 600px wide (or wider). Never upload an image below 400px wide to a 600px template — the result will look pixelated or blurry on retina screens.
Several image-related factors trigger spam filters: (1) too high an image-to-text ratio — keep it 60% text / 40% image; (2) single large image with no text — spam filters can't read image content, so image-only emails look suspicious; (3) no alt text on images — proper alt text signals legitimate intent; (4) total email size over 100KB — compress all images. For newsletters, always include a text version of the email alongside the HTML version. Use a reputable sending service (Mailchimp, Klaviyo) rather than sending from a personal Gmail for bulk campaigns.
JPEG for photographic content (product images, banners, lifestyle photos) and PNG for images with transparency (logos on colored backgrounds, icons). Mailchimp supports JPEG, PNG, and GIF. Compress JPEGs to 75–80% quality before uploading — Mailchimp does not automatically compress images after upload, so what you upload is what gets served to your subscribers. A 3MB product photo uploaded directly to Mailchimp will load at 3MB for every recipient.
