Attachment issue after updating to Mailcow 2025-03a

pablitocwb

Hello everyone!

I was using Mailcow 2025-02 without any issues, but after updating to 2025-03a, I noticed that when I send emails with attachments, recipients are unable to download them, regardless of the email client they use. The attachment simply does not appear as available for download.

Has anyone else experienced this issue or found a solution?

I appreciate any help!

pablitocwb

Hi everyone!

I found that the issue with the attachments was caused by the default signature of one of the domains. It was in HTML, and its formatting was corrupting the MIME structure of the message, preventing proper attachment parsing by email clients.

I’m currently using version 2025-03b without any issues.

Thanks to everyone who viewed the message. If you face something similar, it’s worth checking the HTML structure of your signatures.

chip902

This doesn’t seem like a viable solution. Why should I be punished for not being able to add an attachment if someone’s email signature mimetype is corrupted? Mailcow should let me be able to attach a document to send back to someone if they have an HTML signature

skeelkat

Clarification

I had the exact same issue. The OP referred to it as “default signature of a domain”, this is actually the “Domain wide footer” that is causing this issue and not the “Signature” of the email in the classical sense

I hope this helps someone else in future.