The reason why your picture shows up on emails is actually dependent on the email program or service that the recipient is using to view your email. It’s not a universal feature that applies to all email programs.
Typically, when your picture shows up on emails, it is because you have made it public in some way. This could be through a profile picture that you have set on an online service or social media site that is associated with the email address you are using. Many email programs nowadays have integrated features that can pull profile pictures from various sources to display alongside email messages.
For example, if you have a Gmail account and have set a profile picture on your Google account, that picture may show up when you send emails to recipients who are using Gmail or other email programs that support this feature. Similarly, if you have a Microsoft account and have set a profile picture on Outlook or any other Microsoft service, it may be displayed when you send emails to recipients using Microsoft email programs.
It’s worth noting that not all email programs or services support displaying profile pictures. If you send an email to someone using a program that doesn’t have this feature, your picture won’t show up. Additionally, recipients can often choose to disable the display of profile pictures in their email settings, so even if a program supports it, they may not see your picture if they have opted out.
In my personal experience, I’ve noticed that my profile picture shows up on emails when I use email programs or services that support this feature. It can be a nice way to personalize your emails and make them feel more personal, especially if you frequently communicate with people in a more social or casual context.
To sum up, the appearance of your picture on emails is not something you have direct control over. It depends on the email program or service being used by the recipient and whether they have enabled profile picture display. By making your picture public or setting a profile picture on an associated online service, you increase the chances of it showing up in emails sent to recipients who use compatible email programs.