Any cross-platform email client?

Question

I have been searching for a good cross-platform email client for a really long time. Here are my requirements and a few shortcomings of popular clients.

Requirements:

1. At least available on Android, Linux, Windows 10.
2. At least support both personal and organizational accounts for gmail and outlook.
3. Email-accounts synchronization. I only have to set up my 6 email accounts in 1 device, and all other devices should have access to those accounts without any further configuration on other devices.
4. Able to send, receive, forward, reply, delete, archive emails on all devices, which may contain image, file, hyperlinks and, very importantly, appointment/meeting/schedule invite.

Problems:

1. Outlook does not support Linux or accounts sync. It also has some problems with my gmail university account.
2. thunderbird does not support sync. No Android.

Please let me know if clarification needed.

Answer 1

I'm not aware of any traditional (offline capable) mail client that could do that.

Some web-based solutions might be useful here. They'll work on all of the above platforms though might pose some challenges when it comes to using the interface from a mobile phone.

Web-based clients include:
- Roundcube (does not seem to do calendar stuff)

Answer 2

For desktops, Thunderbird is a great tool.

I use is professionally for sync with different services, e.g. LDAP email sync, caleder sync with yahoo.com, email sync with yahoo.com, email sync with web.de and hotmail.com

Thunderbird supports calender sync with appointments using lightning addon. If you're on linux, install the lightning addon using the command line.

For Android you can try sync your mailboxes with Google mail server.