While on on the subject of Protonmail and PGP keys. You should upgrade your Protonmail PGP keys. The default key size at Protonmail is 2048 bits, which is fine now, but may not be in a few years. The current recommendation by security experts is to use 4096 bit keys.
Most importantly, you should change it to 4096 before sending your keys to everyone so they store the newest key.
To see your current keys and upgrade them if necessary, go to Settings, then Keys. The middle column shows the key type and size.
If yours is not 4096-bit, click “Add New Key”. Then select which email address is getting the new key. On the next screen, select “Highest security (4096-bit)” and click “Generate”. Enter your login password (the first password you enter when login in to Protonmail) After a minute, your new key will show on the web page.
Now we need to make the new 4096-bit key your primary key. Under the Actions column, next to your new 4096-bit key, click the down arrow (∨) next to Export. Select “Make Primary”. Leave the old 2048-bit key active so older key users still work.
Your Protonmail is more more secure. If you have multiple addresses on your account, you may want to upgrade them too.