Хранилище iPhone 11

Which email account are you referring to? Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

Meanwhile look at the settings on Mail Days to sync

On the iPhone there is an option called "Mail Days To Sync." / "Remove After" This option allows you to save space on your iPhone by telling the server to stop pushing emails to your phone. There are several options to select: "No Limit" -- This option will send all the emails in your inbox and folders to your iPhone

Most mails will follow this sequence

Settings > Password & Accounts > iCloud > Mail (Scroll Down) > Advanced > Remove [Select from the options]

Settings > Password & Accounts > AOL > Account > Advanced > Remove [Select from the options]

Settings > Password & Accounts > Yahoo > Account > Advanced > Remove [Select from the options]

Except for Outlook

Settings > Password & Accounts > Outlook > Mail Days to Sync [Select from the options]

Watch the GIF below

Unfortunately Gmail does not have this option at all under iOS Mail app.

However that shouldn't bother you. because it hardly consumes space Settings > General > iPhone Storage > Mail App > [how much is it?] See the GIF below on my iPhone 6

Have you configured POP3?

POP3 tends to use more storage on your device compared to IMAP.

Here's why:

• Storage Location: POP3 downloads emails entirely to your device, while IMAP keeps them on the server and only downloads the content when you view them. So, with POP3, the emails themselves physically reside on your phone, taking up space.
• Offline Access: Since POP3 downloads everything, you can access emails even without an internet connection. This downloaded copy uses storage space. IMAP, on the other hand, requires an internet connection to access emails because they're stored on the server.

However, this advantage of POP3 in terms of storage comes with downsides:

• Limited Accessibility: Since emails are downloaded to a single device, you can't access them from other devices like a laptop or tablet unless you download them again.
• No Synchronization: There's no synchronization between devices with POP3. If you delete an email on your phone, it won't be deleted from the server, and vice versa. This can lead to duplicate emails or confusion.
• Local Management: You can't organize emails on the server itself with POP3. You can only manage the downloaded copies on your device.

In summary, while POP3 uses less device storage, IMAP offers more flexibility and keeps your emails organized and accessible across multiple devices. If storage space isn't a major concern, IMAP is generally the preferred option for most users.