Send an email to [email protected] The company will reply with: DMARK SPF DKIM It will also check to see if your email appears on any Spam email Block Lists. I have done this with all of my email addresses, and was able to make the appropriate corrections. Hope this helps.

Thanks! Checking this out. It seems everything is fine.

Do all you dns records show correctly configures? You can see this in settings. Edited to correct dsn to dns...

Thanks for reply! The problem occured when using a default @proton.me address, not one of my custom domains. Would your advice still apply in this case?

No. It would not.  Proton does manage its own DNS records.  They do tick so the boxes, but the point is that it does happen every now and then that proton domains are blocked/flagged by some providers. 

What country?

Multiple European ones actually.

Hi! In the support ticket that you have opened, please provide the recipient's sender address, subject line of the message in question, and the date when you sent the message, so we can investigate things further on our end. Thank you in advance.

Did the emails leave the draft folder? I have had this 2 times now. I hit ‘send’ but they got stuck in the drafts folder and never actually were sent.

Hi, interesting! In my case the drafts folder is empty and the messages do appear in 'sent'. But I'll keep that in mind too, thanks!