Gmail refuses attachments larger than 25 MB, and Outlook-style mailboxes have similar limits, so a phone video often has to shrink before it can be emailed.
Aim a little under the limit: email adds overhead to attachments, so a 24 MB file is safer than one sitting right at 25 MB. This tool already leaves a margin. The tool aims for roughly 93 to 95 percent of the limit so the finished file does not tip over it.
Need a different ceiling? Use the related pages for other common upload caps, or the general FileHost.net Video Compressor for manual quality control.