How does SER handle a refused POP3 login when two projects check one mailbox?

Hi all. Full disclosure first: I'm building a catch-all mail service for SER users, and I want it to behave well with SER before I offer it here.

The question. Our POP3 server allows one session per mailbox per IP, so two projects can't take the same message or delete it from under each other. A second login made while the first is still open gets a plain `-ERR` (connection limit). The slot is free again a fraction of a second after the first session logs out.

What does SER do in that case?

- retries the email check later;

- or marks the email account as failed / bad login and stops using it?

If anyone has seen this with any catch-all or POP3 provider that limits connections, I'd be grateful to hear. It decides whether we should answer differently, for example with `[IN-USE]`.

And a rules question: the service was built for this forum's audience, and I'd like to offer it properly in Buy / Sell / Trade, but I don't have 30 posts yet. Is a PM to s4nt0s the right way, or should I contribute here first? No links in this post on purpose.

It will "retry the email check later".

But there is also an option to allow to login only ones per login. So it would not come to an ERR message.