Slow image loading in Outlook email

Slow loading images in PoliteMail v4 using hosted images (PoliteMail > Add Image)

When viewing an email, Outlook will usually multi-thread content loading (many at once), *sometimes* Outlook will single-thread (one-at-a-time) content/image loading (e.g. if Outlook is busy talking to Exchange, has multiple windows open, etc.).

Then this single-threading occurs, the PoliteMail read-timing image may load ahead of another larger image, and the display of that other image will wait for the read-timer to complete (200% of content length). This would create the effect of the image being temporarily broken (gray box in Outlook) or not loading.

The work-around/temporary resolution is:
As larger (typically header), images tend to be slower (and the PoliteMail read-timer is tiny, but purposely slowed), they may fall behind in the load-thread requests when Outlook decides to single-thread. If you paste header images into the templates, and use PoliteMail add-graphic images for the other images– then the recipient will always see the header image (note: some non-Outlook email/mobile email clients show embedded images as file attachments) which prevents the *broken email* appearance and the message still retains the ability to measure read-time and host other images to keep the file size reasonably small.

Root cause/permanent resolution: This is an Outlook bug/feature which switches to single-threading, and when combined with the PoliteMail read-timer slow-loading (once it happens on a message, seems to continue on that one message on that machine). PoliteMail is working through its MS Partner program to document and submit the issue to the Microsoft development team.