How can my friend bypass the spam filter?
Our spam filters are extremely reliable, but in rare cases you might find that someone who sends you mail is using a mail server that's listed in an anti-spam blocklist. This can happen if the people who run that server allow it to be mostly used to send spam, even if your correspondent is not actually a spammer.
However, if you do that, you will receive much more spam. If you don't wish to turn off the spam filter entirely, a better idea is to create a special forwarding address and tell the person to send to that address.
For example, if your normal address is email@example.com with the spam filter set to "High", you might create firstname.lastname@example.org as a forwarding address that forwards to email@example.com but has the spam filter turned off.
As long as you keep the extra address secret, spammers will not find out about it: your correspondent will be able to write to you and spammers won't. Don't put the secret address on a Web page or anywhere else that a spammer might find it.