What is the file size limit of an attachment to an SMS or an Email?

SMS carriers and Email Providers have attachment file size limitations to prevent deliverability issues and to make sure that their servers are not overloaded with hefty file sizes while millions of people around the world use their services to send SMS and Emails.

SMS
To send attachments, your Twilio phone number should be MMS enabled. We support up to 10 attachments, as long as the total size of the message body text and all attachments is less than 5 MB.

Carriers also have limits. The average is 300kb-600kb and can go up to 3.5MB for tier 1 providers (AT&T/Verizon, etc.).

Here are the Carrier Attachment Size limits for some common US Carriers:

The file sizes above will generally be passed along to the wireless carriers. However, due to differences in handsets, file types, and transcoding, we recommend you send attachments no larger than 500KB to ensure the best chance of delivery.

These image file types are supported:

• jpeg
• png
• gif

Please Note: As of May 2021, there is an issue with Toll-Free MMS file size support; for these numbers, you must ensure that any attachments (including images) are 600kb or smaller.

Email
Mainly for security reasons, all email server providers limit the maximum email size that an email account can receive. Otherwise, if there would be no maximum email size limit, the email server would risk being bombarded with very large emails, causing it to cease working properly.

Some free email address providers also enforce commercial limitations on the email size: the free account gets a low maximum email size limit, but you can increase the maximum limit by upgrading to a paid account.

If you send an email that exceeds the maximum email size limit of the recipient’s email provider, your email will bounce back, and you will receive an email error in your Conversations tab. Usually, you will receive one of the following error messages:

• “Attachment size exceeds the allowable limit”;
• “552: Message size exceeds maximum permitted”;
• “System Undeliverable, message size exceeds outgoing message size limit”;
• “The size of the message you are trying to send exceeds the global size limit of the server. The message was not sent; reduce the message size and try again.”

Mailgun supports maximum message sizes of 25MB.

Here are attachment sizes for different Email Providers.

FAQs:

Can I send mp4 files via SMS?

• MP4 files are supported for sending as MMS attachments. If you attach an mp4 file, it should be sent as an MMS. However, MP4 files cannot be attached directly when sending SMS. If you record a video in the mobile app, it will generate a link to the video recorded so the contact can click on it to view the video.

Can you bypass these maximum email size limits?

• A simple answer would be: no, you can’t bypass these maximum size limits. However, there is a workaround:
• You can upload the files-to-be-attached to cloud storage servers (like DropBox, Google Drive, or SkyDrive) and include the download link in your email.