Handling File Attachments in eForm Without Breaking Validation

This donor was a substantial eForm example: a contact form with validation messages, captcha, and an attachment input, all running on an older Evolution build where plain mail and SMTP behavior could differ.

Why attachment forms become tricky

• multipart form encoding must be correct
• mail transport and attachment handling must agree
• validation, captcha, and file UI all add state to the same form
• host limitations can make a correct form still fail in practice

What to keep stable

For forms like this, keep the flow disciplined:

• use enctype="multipart/form-data"
• keep attachment handling explicit and predictable
• validate text fields and captcha before the mail layer runs
• test attachment delivery on the real host, not only locally

The broader lesson is that a “simple contact form” stops being simple as soon as it accepts files. At that point, transport, validation, and UX all need to be treated as one coordinated flow.