[quote user="Brian Fluet"]

I appears that FastMail supports app passwords which should work with Pegasus Mail.

https://www.fastmail.com/help/clients/apppassword.html

[/quote]

Thank you.  I may use that procedure.

I received this message yesterday from Fastmail my IMAP email provider:

" The server insecure.messagingengine.com has allowed Fastmail accounts
to connect to programs that could not support up-to-date encryption
methods, such as older email clients, CRM systems, and printer or
scanners with a "scan to email" function. We have made it available in
the past as a convenience to users who otherwise would not be able to
connect to their email client or program.

Unfortunately, maintaining this server is preventing us from making
certain security upgrades. For this reason, we will be removing
insecure.messagingengine.com on February 3, 2020, and any clients or
other programs using this server no longer be able to connect.

If the client or program you’re using can support newer encryption
methods, we expect you will be able to continue to connect by using
our updated server names. For details, please see [our help page for
server names and
ports](https://www.fastmail.com/help/technical/servernamesandports.htm
l)."

Does anyone have any information about this?  

Is there any information about how Pegasus Mail will

Have you read their info page on two factor authentication? And if so are you prepared to do the setup to implement it?

https://www.fastmail.com/help/account/2fa.html

I appears that FastMail supports app passwords which should work with Pegasus Mail.

https://www.fastmail.com/help/clients/apppassword.html

Yes, I looked into that procedure.  I don't know if that's how I want to proceed.  Sorry, this was posted without quotes from Irelam's message.