One quiet December morning, with the office already emptying out for the holidays, a ticket lands on BlueMind’s support desk. A company can no longer send its purchase orders to partners. Every message is silently rejected. The IT team looks for malware issues, checks logs, blames the firewall. But the problem lies somewhere far more mundane: the email simply exceeds the maximum size allowed somewhere along its delivery path.
We tend to think of email as light and instantaneous — one click and it’s gone. Yet a message can quickly become a heavyweight, especially when large attachments or over-designed signatures creep in.
This article walks through why emails get so big, where the bottlenecks appear, and how BlueMind helps you avoid these pitfalls.
Invisible weight, real consequences
The maximum size an email can reach before being rejected is determined by the smallest limit anywhere on its route — your outgoing server, intermediate relays, ISPs, and finally the recipient’s server. If the message exceeds any of those thresholds, it will be bounced. Most organizations set their limit somewhere between 10 and 20 MB. You can choose a higher ceiling internally, but there’s no guarantee your recipients will accept larger messages.
A typical policy caps messages around 15–25 MB, attachments included. In reality, that’s far less room than one might think.
Take a 15 MB PDF. Once attached, it is encoded in Base64 to travel through SMTP, instantly inflating its size by roughly 33%. Your “15 MB” PDF now weighs about 20 MB inside the final message.
Add to that:
- email headers
- the HTML body
- authentication metadata (SPF, DKIM…)
- tracking elements
- and your signature — often packed with hidden heavy images
…and you’ve easily crossed the limit without even realizing it. Mail clients don’t warn you, because they don’t know the constraints imposed by the servers along the way.
When that happens, the message never reaches its destination. The sender receives a cryptic bounce message filled with technical jargon. The main culprits are almost always attachments and images. Text barely weighs anything. Images, on the other hand, often represent 99% of an email’s weight — including those tiny logos in signatures that aren’t tiny at all.
BlueMind: send large files without breaking email
To prevent oversized-email issues, BlueMind offers a native large file delivery feature. Instead of embedding the attachment, BlueMind automatically stores it in a secure space (on your server or drive) and replaces it with a download link. The link is unique, protected, and compliant with your organization’s security policies. For the recipient, nothing changes: they click and access the file. For the sender, the gesture is identical to attaching a document.
As soon as a file exceeds the size set by your administrator, BlueMind offers to upload it to the drive and insert a link. The message remains light and effortlessly makes its way through all intermediate servers. This feature is fully customizable — by file size, recipient type, or internal security policy. It also helps reduce mailbox sizes, storage pressure, and archive load.
If the file is smaller than the detachment threshold, users can still choose between a traditional attachment or a link. When your organization uses a connected drive (Hexagone, eXo, Nextcloud, GoFast…), BlueMind stores and links directly from that environment.
Centralized, lightweight email signatures
Managing user signatures is usually a nightmare. Without a dedicated tool, the communications team provides an HTML template, hoping employees will install it correctly… and keep it as-is. The result is often a parade of homemade banners, oversized images, inconsistent layouts, and outdated logos — all of which slow down email, clutter inboxes, and distort your brand.
BlueMind solves this with centralized signature management. The communications team designs a clean, lightweight, mobile-friendly signature and assigns it to an entire department or the whole organization. Temporary campaigns can be scheduled: event banners appear for the exact duration required, then disappear automatically.
Users no longer tinker with signatures, storage usage drops, and the company’s identity finally remains consistent. BlueMind even lets you disable corporate signatures for internal emails or use a simplified internal version — preventing visual overload in thousands of everyday messages.
Conversations : one thread to rule them all
Every time someone clicks “Reply”, a few new lines are added… but the entire previous thread — all messages, all signatures, all attachments, all logos — is resent. Two new sentences can trigger the re-transmission of what amounts to an entire book.
BlueMind’s conversation mode curbs this inflation. Messages belonging to the same exchange are grouped into a single visual thread. One click unfolds the entire history, without forcing you to open multiple emails to understand the context.
Users can still organize individual messages into different folders without generating duplicates on the server. Conversation view clarifies ongoing exchanges, makes the inbox lighter, avoids duplications, and reduces the hidden weight carried forward with every reply. It also offers flexible display options, letting users choose chronological or reverse order reading.
One email, a thousand details
As we’ve seen, the size of an email has real consequences on deliverability, performance, storage, and cost. A 500 KB signature, a handful of oversized attachments, a conversation thread turned into a makeshift document vault… and your messaging system becomes heavier, slower, and more expensive to maintain.
Most of these issues come from bad habits: using email as a document repository, keeping working drafts indefinitely, multiplying recipients “just in case”, or allowing users to manage their own signatures.
A few simple practices go a long way:
- emptying trash regularly
- limiting unnecessary CCs
- not storing non-final documents in email
- keeping signatures concise and optimized
For these good practices to stick, you need the right tools — ones that fit naturally into everyday work. BlueMind already provides several features to promote lighter, smoother email usage, and will soon offer automatic cleanup of old items. A collective effort keeps messaging reliable, fast, and sustainable.
At BlueMind, we don’t just deliver email. We help ensure your messages actually arrive — securely, efficiently, and without compromising user comfort.
