I've loved using Pegasus Mail these past 30 years, since I found it 1991, but I now fear my emailing future - due to what the internet companies are imposing on users like myself in the supposed interests of safety and security.

Pegasus has always worked brilliantly for me but just recently my ISP (Yahoo) has begun refusing CCs and/or BCCs to certain addresses when I am using Pegasus. At such times Pegasus now shows me a message about alleged "pipelining". I've yet to work out how to get round this problem. I know, however, that it's to do with restrictions introduced by either the ISP or one or more of the tech companies.

For my Android device the closest email client I've found to Pegasus has been K-9, which I've been using for about 10 years, although it's nowhere near as sophisticated as Pegasus. But K-9 too has now begun presenting some emailing difficulties due to decisions taken by the tech companies.

At this moment I am finding the Yahoo app the most reliable email client in terms of immediate sending and receiving, but the Yahoo app is so pathetically basic, and like K-9 it doesn't allow me to manage all my incoming and outgoing emails in detail.

I have the Gmail app on my Android device too, and it's reliable, though not as rapid for me as the Yahoo app. But I have a dreadful feeling that Google has manipulated matters so that come the end of May, or some point thereafter, I may have to use Google's Gmail app only for trouble-free sending and receiving. One reason why being confined to using Gmail irks me is that I don't want Google being in possession of all my contacts information and every email I have sent and received until such time as I log into their site and delete material. I much prefer to keep things "local", on my own computer.

So I hope that come the end of May I will find some way of emailing so that I will continue to use Pegasus Mail as my primary email client, even though my emailing life may no longer be as trouble-free as it used to be.

I would be interested to hear if any of my above thoughts strike chords in other Pegasus users.

I can't relate to this post.
Firstly, I don't know if the issue with Yahoo and pipelining is related to Pegasus Mail but since you don't think so, it disturbs me that it is included in this post rather than a separate post requesting help or advice.
Secondly, Pegasus Mail is a Windows program. All references to "app" and "Android" are irrelevant.
Thirdly, my two Gmail accounts work fine with Pegasus Mail and I expect them to continue to work fine after the end of May. The current workaround to Google's upcoming OAUTH2 requirement is to use an app password.

Surely you can at least relate somewhat to "I've loved using Pegasus Mail these past 30 years . . . Pegasus has always worked brilliantly for me . . . it's nowhere near as sophisticated as Pegasus . . .".

You quoted these phases out of context. They all contained a "but" that I don't relate to.
"I've loved using Pegasus Mail these past 30 years, since I found it 1991, but I now fear my emailing future..."
"Pegasus has always worked brilliantly for me but just recently..."

I can't relate to this one either since I have never run K-9 on an Android device.
"For my Android device the closest email client I've found to Pegasus has been K-9, which I've been using for about 10 years, although it's nowhere near as sophisticated as Pegasus."

I admit that Pegasus Mail is showing its age. I also hate that it has been a long time since I have recommended it to anyone. I come from a time when configurability was paramount, where auto-updates were despised, and where simple and clean interfaces were preferred (I still hate the MS Office ribbon). Old IT folks seem to be the only ones who appreciate those things these days.