Following up on my comments above,
Mailwasher is a filtering tool working on headers via POP3, for clarity it downloads the headers and works locally, then deleting the full email at the ISP. You cannot access and work on the ISP server directly other than webmail. Firetrust clearly describe how Mailwasher works in their own faqs
Thunderbird can be set for ...
Browsing through packages available for installation in Synaptic, I found something called pop3browser. From the description:
Allows one to check a pop3 mailbox before downloading any mail
pop3browser is intended to delete unwanted (SPAM) mails before downloading via a low-bandwidth connection. This is useful to save time, bandwidth and space.
You may give ...
Use this program to "Unspam" your mailbox(es).
The program can be integrated with the mail server to automatically filter all mail for a site.
It can also be run by individual users on their own mailbox and integrates with several mail programs.
SpamAssassin is highly configurable; if used as a system-wide filter it can still be ...
I used https://mxtoolbox.com/SuperTool.aspx to study your domain DNS setup and everything looks as expected for the mail server, MX records, and SPF record. You've already met the basic requirements below, and next steps for you are to setup DKIM signing on your email server (and publish the public key) and lastly (and optionally) publish a DMARC policy as ...
Evolution, the standard GNOME e-mail client, also informs about incoming mails via notifications. There is also an additional package, evolution-indicator, that displays notifications even when Evolution application is not currently running.
Good things to try are:
MailNag (fork of Popper), it is installable by
sudo add-apt-repository ppa:pulb/mailnag
sudo apt-get update
sudo apt-get install mailnag
Mozilla Thunderbird with BirdTray, installable by
sudo apt-get install thunderbird birdtray
BirdTray minimizes Thunderbird on start and then monitor its mail folders to indicate number of new e-...
At first you have to inform snap developer about the problem.
Then remove buggy snap'd version with
snap remove mailspring
and download deb-version from the official site and install it instead.
Also note that there are some mature free alternatives like Thunderbird, GNOME Evolution, Geary and others.
As mentioned in the answer by @prosoitos. This is a useful flowchart. From that I solved my issue which threw the same error message.
In my case I was using two-factor-authentication (recommended for security). So as per the flow-chart I simply needed to:
Create a new app password at the MS security settings page and copy it.
In Pidgin open the Modify ...