A modern phone photo is three or four megabytes, so half a dozen of them will not go through most mail servers. Drop them here and they come back small enough to attach, and small enough that whoever gets them can actually open them.
Up to ten. On a phone you can share them straight into this page from your camera roll.
Large enough to look right on any screen, small enough that a mail server will take them.
Download them individually, or take the zip and attach that instead — which most mail clients handle better than ten separate files.
Gmail and most consumer providers stop at 25 MB per message, Outlook.com at 20 MB, and plenty of corporate mail servers cut off at 10 MB. The limit applies to the whole message after encoding, which adds roughly a third — so treat 15 MB of attachments as the practical ceiling on a 25 MB account.
Once these are compressed, comfortably more than you are likely to send in one message. The totals line above the results shows what the set weighs now, so you can check before you attach rather than after the bounce.
On a screen, almost certainly not. These come back as ordinary JPEGs at a width that still looks sharp on a laptop or a phone. If somebody needs to print one large, send them the original for that one.
Not from here. Camera and GPS data are stripped by default, so the copy you attach does not carry the coordinates of your house. That is worth knowing because emailing an untouched phone photo does send them.
Free Online Image Optimizer