Messages disappear from trash (Apple)

By default, the iOS Mail app deletes messages in your Trash folder after one week. Apple Mail sets this default to one month. To change these settings:

iOS

After adding your Fastmail account, you can change the setting for automatically removing deleted messages by going to:

1. Tap Settings on the iPhone's Home screen.
2. Go to Mail, then Accounts. For older iOS versions, tap Passwords & Accounts (or Mail, Contacts, Calendars).
3. Tap your Fastmail account in the accounts list, then tap Account.
4. Scroll to the bottom of the settings and tap Advanced.
5. Tap Remove in the Deleted Messages section, then select Never.

Mac Mail

1. Open Mac Mail, and click Mail → Preferences.
2. Select your Fastmail account from the accounts list.
3. Click the Mailbox Behaviors tab.
4. For “Erase junk messages:” select Never.