The generic AI-generated response above likely doesn't address your underlying difficulty...
For image attachments, the iOS/iPadOS Mail App allows you to choose/select the most appropriate attachment file-size - usually defaulting to the smallest (and therefore lowest quality). You can manually select a higher quality (and therefore larger file-size) while drafting your email. This facility provides significant control, allowing you to keep within the bounds of email size limits.
Having attached your image(s) to your draft email, you'll see something like this - noting that the attached images will show the current attachment file size:

The indicated Images file-size indicator is actually a selector-button.
Tap the button and you'll be able to select the file size that you wish to send as attachment. You should note that the indicated attachment size is the total - so if you have two or more photos attached to your mail, this will represent the combined file-size of the attachments.

In this example, the single photo attachment has defaulted to Small (35.0 KB). Tap any of the other available options to select, noting that the corresponding file sizes are proportionally much greater - the largest here (Actual Size) for the full-resolution photo being 4.1 MB.
Be aware that Mail systems are generally limited in the maximum attachment file size that they will handle. Consider that an email will likely transit many systems before delivery of the mail and its attachments to the recipient. While some email platforms may allow you to send large attachments (e.g., Google Mail - 25MB), many will reject mail attachments of this magnitude. Remember, the Mail server of the recipient may not accept large attachments.
As such, it is generally recommended that you limit your attachment size to 10MB or less - as a delivery failure is perhaps less likely.
For particularly large attachments, or bulk sending, you might be better advised to host the photos on a recipient-accessible platform - and simply send a link to the file(s). Many free (or paid) cloud-services are useful for this.