Referring to attached images in html email body through mailx

encoding type for images?

Please read the forum rules again:

Just search for "mailx attachment"

what is the encoding type for images?

That's got nothing to do with mailx, but is universal for all inlined images in emails.

When attaching the image, give it an unique content-id, which you can then reference using <img src="cid:your-id-here" />

Reference

encoding type for images?

what is the encoding type for images?