Fastmail is currently undergoing an outage. Their status page linked below currently shows an outage for outgoing mail but I am experiencing problems using search and downloading attachments too.
August 29, 2024 at 3:51 PM
We now believe that all of our outbound traffic is experiencing significant disruption.
We are continuing to investigate the problem.
August 29, 2024 at 3:00 PM
Fastmail maintains a number of server addresses for TLS-secured IMAP, POP, and SMTP connections intended to deal with blocked ports in a user's local network: https://www.fastmail.help/hc/en-us/articles/1500000279921-IMAP-POP-and-SMTP#01H8Q4K5PQ0TNBQXT458TA4083
These servers are currently experiencing an outage, i.e. the following addresses can not be reached:
imaps-proxy.fastmail.com
pops-proxy.fastmail.com
smtps-proxy.fastmail.com
We recommend users to switch to one of the regular services if they can reach them at:
IMAP: imap.fastmail.com Port 993
POP: pop.fastmail.com Port 995
SMTP: smtp.fastmail.com Port 465 (SSL) or 587 (STARTTLS)
We are investigating the issue and will work to resolve the outage as quickly as possible.
https://fastmailstatus.com/