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How can I optimize inline images in Limesurvey invite emails to avoid Outlook blocking? Despite using PhpMailer's AddEmbeddedImage, direct image links (hxxp://www..../xxx.jpg) trigger blocking. Is there a fix or a smooth transition to SwiftMailer for a more efficient solution?

After uploading you image replace the link to /upload/suveys/XXXX/image.jpg

Remove the base url

ok but I have one another question that I have large size of jpeg images and does limesurvey automatically compress jpeg images or I should compress first our image file with third party application such as ***** and we should upload our images.

You should compress yourself use any image edit tool.