Sending more than 15 or 20 pictures by email

Every ISP has a maximum limit on attachments. If I have to send several, I uaully just split them up and send several emails. There are iClouds maximums:

iCloud: Mailbox size and message sending limits - Apple Support

Check with your other email providers and/or ISP to check on theirs.

An alternative might be to utilize your iCloud account's Photo Album features... you can create a Shared Album and invite others to view it in an email via a link.

iCloud Photo Sharing FAQ - Apple Support

Feliz Año Nuevo

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You could also upload them to something like Flickr and then let your recipient download them at their leisure.

You can do it with 3rd party apps like Photo Manager Pro.

https://appsto.re/sg/c4CEx.i