Attachment Size Limits for Open Doors Phone SMS/MMS & Email

Open Doors Phone · Conversations · AttachmentsAttachment Size Limits for Open Doors Phone SMS/MMS & EmailUnderstand file size limits for Open Doors Phone SMS/MMS and email, how larger files are handled, and when attachments are delivered directly or through Media Library links.Overview

This article explains attachment size limits for SMS/MMS sent through Open Doors Phone and email. It also explains how the system uses the Media Library to handle files that cannot be delivered directly and how attachment behavior differs between messaging channels.

What are File Size Limits for Open Doors Phone SMS/MMS and Email Attachments?

Attachment size limits determine whether a file can be delivered directly through Open Doors Phone MMS or email or must be shared another way. Understanding these limits helps reduce delivery failures and clarifies when it will use a Media Library link instead of sending the original file as a direct attachment.

Table of Contents1Key Benefits of Understanding File Size Limits2Open Doors Phone SMS/MMS Attachment Size Limits3Email Attachment Size Limits4How to Upload Attachments in Conversations5Paste Attachments from Clipboard6How to Send Larger Files7Frequently Asked Questions8Need Help with Open Doors Phone Attachments?1

Key Benefits of Understanding File Size Limits

Knowing attachment limits helps you avoid failed deliveries and understand when files can be sent directly or should be shared through the Media Library.

• Improved Deliverability: Reduce delivery issues caused by attachments that exceed supported Open Doors Phone or email limits.
• Clearer Channel Requirements: Understand how attachment handling differs between Open Doors Phone SMS/MMS and email.
• Simplified File Handling: Use the Media Library for files that cannot be sent directly.
• Fewer Manual Workarounds: Reduce the need to compress files or use third-party hosting.
• Better Engagement: Use supported video thumbnails and file links to make messages easier for recipients to access.

2

Open Doors Phone SMS/MMS Attachment Size Limits

SMS sent through Open Doors Phone supports text only. When supported media is sent directly with a text message, the message is delivered as MMS. If a file cannot be sent directly because of its size, file type, or delivery requirements, you can use the Media Library to share the file through a clickable link instead.

Commonly supported image types for direct MMS include:

JPEGPNGGIFPlease Note

Other media types, including MP3, MP4, and PDF, may be handled differently depending on the carrier, recipient device, and whether the file can be delivered directly through Open Doors Phone MMS. Files that cannot be delivered directly can be shared through a Media Library link.

Part 1Carrier-Specific File Size Limits for MMS

Carrier and number-type limits can vary when sending MMS through Open Doors Phone. For the broadest compatibility, keeping direct MMS attachments under 500 KB is a conservative best practice, even when a higher technical limit may be supported.

Carrier	Long Code MMS	Toll-Free MMS	Short Code MMS
AT&T*	1.0 MB	0.6 MB	0.6 MB
T-Mobile	1.5 MB	0.6 MB	1.0 MB
Verizon	1.0 MB	0.6 MB	1.2 MB

Part 2Long Code, Toll-Free, and Short Code MMS Support

Open Doors Phone can support MMS using applicable Long Code, Short Code, and Toll-Free numbers. The maximum supported file size can differ by carrier and number type, so the values below should be treated as upper limits rather than guaranteed delivery thresholds.

Message Type	Supports MMS?	Maximum Size Reference
Long Code (10DLC)	✅ Yes	Varies by carrier
Short Code	✅ Yes	Up to 5 MB
Toll-Free	✅ Yes	Up to 5 MB

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Email Attachment Size Limits

The system limits the size of files that can be attached directly through the email composer. Recipient or sending email providers may also apply their own restrictions, so keeping attachments within the composer limit helps reduce delivery issues.

Good to Know

The email composer allows up to 20 MB in direct attachments. Files above this size are uploaded to the Media Library and shared as clickable links instead of being sent as direct email attachments.

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How to Upload Attachments in Conversations

It lets you attach files directly from your device or select existing files from the Media Library while composing an Open Doors Phone SMS/MMS or email in Conversations. The steps below show where to access these options.

Step 1Access the Attachment Options

Open a conversation under the Conversations tab and click the three-dot icon (•••) in the message composer.

Step 2Choose Your Attachment Source

After clicking the three-dot icon, select Attach Files. You'll see two options:

Upload from System, choose a file from your local device.Choose from Media Library, select a previously uploaded file.Step 3Automatic Handling for Files That Cannot Be Sent Directly

For email, files above 20 MB are uploaded to the Media Library and inserted into the message as a clickable link.

For Open Doors Phone SMS/MMS, files that cannot be delivered directly because of their size, type, or channel requirements can also be shared using a Media Library link.

Important

Video Uploads Get Auto-Generated Thumbnails. When a video file is uploaded through the Media Library for use in email, it can generate a GIF thumbnail that gives recipients a visual preview and clickable entry point to the video.

5

Paste Attachments from Clipboard

Clipboard pasting provides a faster way to attach a supported file or image without opening the attachment menu.

1. Copy a supported file or image on your computer.
2. Click inside the message composer in Conversations.
3. Press Ctrl + V (Windows) or Cmd + V (Mac), or right-click and select Paste.

The pasted file is added to the current message and follows the same Open Doors Phone SMS/MMS or email attachment-size and delivery rules described above.

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How to Send Larger Files

Large files do not always need to be compressed or hosted outside the system. The Media Library provides a way to share files as links when they exceed direct Open Doors Phone MMS or email attachment limits.

• Upload the file through the Open Doors Phone SMS/MMS or email composer.
• Email files above 20 MB are hosted through the Media Library and inserted as clickable links.
• Open Doors Phone SMS/MMS files that cannot be delivered directly can be shared through a Media Library link.
• Use external cloud hosting only when the file needs to be managed outside.
• Use Media Library video uploads when you want to generate a visual thumbnail for email.

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Frequently Asked Questions

Q: Does a file uploaded to the Media Library have the same limit as a direct Open Doors Phone MMS or email attachment?No. Media Library storage and direct message-delivery limits are different. A file may be stored in the Media Library even when it is too large or otherwise unsuitable to send as a direct Open Doors Phone MMS or email attachment.Q: What will the recipient see when the system hosts a file instead of attaching it directly?The message contains a clickable link to the hosted file instead of delivering the original file as a direct attachment.Q: Does adding supported media always keep an Open Doors Phone message as SMS?No. SMS is text-only. Supported media that is delivered directly through Open Doors Phone changes the message to MMS.Q: Why can a file be stored in the CRM but still fail as a direct Open Doors Phone MMS attachment?Media storage limits and carrier-delivery limits are separate. Carriers can impose lower limits on direct MMS delivery than the file sizes the system can store.Q: Are Open Doors Phone MMS limits guaranteed to be the same across all carriers?No. MMS limits can vary by carrier and number type. Keeping direct MMS media relatively small improves compatibility across networks.

Need Help with Open Doors Phone Attachments?

If an attachment does not send or display as expected, checking the file size, file type, and delivery method can help identify whether the file should be sent directly or shared through the Media Library.

Before Contacting Support

• Confirm the file type is supported for the intended message channel.
• Check whether the file exceeds the recommended direct MMS or email attachment limit.
• Try sending the file using a Media Library link if direct delivery is unsuccessful.
• Review the conversation for any delivery or attachment error message.

Still Need Help?

If the attachment continues to fail after checking the file size, type, and delivery method, contact Support from within the platform. Include the file type, file size, message channel, recipient details, exact error message, and a screenshot or screen recording of the issue when possible.