Fix the email reception on the local server in SnappyMail

🔧 Technical Specification

Problem:
The server correctly receives regular emails, but emails with attachments (for example, images) do not arrive at all — neither through Amazon SES inbound nor directly. They are not present in the Postfix and Dovecot logs.

What has already been done:

• Server: Ubuntu 24.04, Postfix + Dovecot

• Mail reception via Amazon SES Inbound (MX: inbound-smtp.eu-north-1.amazonaws.com)

• SnappyMail in /var/www/html/snappymail (web interface is working)

• Amazon SES Webhook PHP handler is connected (works with regular emails)

• message_size_limit = 0 set in Postfix

• Checked: emails from Gmail with images bounce back with bounce: 552 5.2.3 Message length exceeds limit set by recipient

Need to:

1. Determine which component (Postfix, Dovecot, SnappyMail, or PHP) is blocking emails with attachments.

2. Configure proper reception of all emails, including:

   • With images (Content-Type: multipart/related)

   • Replies to emails (with inline graphics)

3. Ensure that emails with attachments are delivered and displayed in SnappyMail.

4. Check that Amazon SES does not block delivery due to server limits.

5. Ensure logging of deferred/deleted emails (just in case).

Preferably:
Explain what was the cause so we can avoid it in the future.

In general, I will be contacting often. If you are a professional, I am waiting for you.

No AI work, only professionals please. I spent the whole day with it myself, and it couldn't help.