The mailbox size for a Freenetname account should actually be 250MB, but I appreciate it's still rather small. I'm afraid that we can't increase this or offer an alternative, so it may be best to move your domain to another registrar and host.
If you'd like to go ahead, send me a private message with your account username, domain name, and the IPSTAG of new registrar. I'll then create a ticket you can respond to with confirmation before raising this to our NetOps team to transfer your domain across. Your existing emails won't follow you though so you'll need to back them up.
From 31st October 2022, I no longer have a regular presence here as I’ve moved on to a new role.