There are several limitations and restrictions that impact the creation of email templates.

Characters in names

In folders, databases, queries, emails, and email names, only spaces and the following characters are allowed:

• A-Z
• a-z
• 0-9
• # - _ ( ) '.

Code validation

The web compose editor does not check, validate, or rearrange the HTML code. Anything that you enter remains just as you entered it. No validation of the HTML or CSS markup is done by the editor. For best performance of email message code, conform to W3C specifications and be aware of the limitations of your customers' email clients. You can check your code on this free website: W3C Markup Validation Service.

Scripting languages

The use of JavaScript™, PHP, or other scripting languages for server-side or client-side processing is not supported.

Attachment size

The limitation on file size of attachments is entirely up to individual ISPs. The upper limit is typically 10 MB, but some networks might block anything over 2 MB. We recommend with files that are larger than 10 MB that you host the file somewhere and add a referring link in the body of the email.

If you have the file available on a landing page that you create in, you can track the download of that file and activity on that page as well. We recommend that you use this method because large attachments can cause problems for email clients.

Email size

There is no hard limit for the message size, but message file size can have a direct impact on the success of an email. Large image sizes can impact the success of your email. If you use the asset library to upload your images into your email template, format the images to a smaller size before you upload them. For images in your template that you directly upload from your hard drive, resize them to lower the size of its overall contribution to your email.

If you send messages over 120 KB, your messages might be blocked or filtered by various ISPs and email clients. If the message is delivered, the reader might be suspicious of its size, thinking there might be a virus hiding inside. Ideally, the message should be smaller than 75 KB and around 35 KB is recommended.

Link names

The only valid characters in a link name are letters, numbers, underscore, and spaces. Any other characters cause an error.

Seed list recipients

Because they are based on production lists, the following email features don't work for seed list recipients:

• Personalization
  Based on list fields in the production list.
• Dynamic content
  Based on list fields in the production list.
• Forward to a friend
  Tracked based on membership in the production list.
• Share to social
  Tracked based on membership in the production list

Server side includes

Server side includes or SSIs are not supported.

Restrictions

An email faces a restriction if the delivery failed because of a problem with the message, not with the address.

There are three common reasons for email to be placed in this category:

• The recipient does not accept mail with attachments.
• The message is too long.
• The message is improperly constructed, which can be the case if you create a proprietary message-generation engine.

Restrictions by country

Your emails might not function correctly in the following countries:

• Cuba
• Iran
• North Korea
• Sudan
• Syria

If people in any of these countries receive your emails, they can't click anything within the email and it might not render properly in their inboxes. This also affects users who try to access while they are traveling in any of the above countries.