7.4.11. Attachments not showing on receiver's side when sending campaign emails

Suite 7.11.4. Attachments are not showing on receiver’s side when sending campaign emails. But when sending the same template as a single mail with mail composer, the attachment comes with the message on the receiver’s side. Don’t know if there is a relation but this issue emerged after installing and successfully uninstalling a module from the SuiteCRM marketplace that validates email addresses.