I do this and it works fine though there are some limits to be aware of (see "Quotas for other services" https://www.fastmail.com/help/account/limits.html https

I do this and it works fine though there are some limits to be aware of (see "Quotas for other services" https://www.fastmail.com/help/account/limits.html https://www.fastmail.com/help/account/limits.html).