Serious issues receiving all emails forwarded to Yahoo mailbox

[vjayer]

Prerequisites

• [X ] I have searched open and closed issues to make sure that the bug has not yet been reported.

Bug report

Describe the bug
Recently, for many aliases, it takes at least an hour, to well over an hour (.. in one instance it look about 12 hours! ) to forward emails to my Yahoo mailbox--or for Yahoo to deliver it to me after receiving it.
And all emails always end up marked as Spam. Marking as "Not Spam" (so far a couple times) does not seem to help as far as the massive delay in receiving the emails at Yahoo. I am testing using gmail as sender.

And for one of the custom [e-mail], which I originally used for a service's newsletter email, I cannot receive any of the forwarded emails sent to that address AT ALL now. A few came in the past, but now when I try to test that custom [e-mail] I used for their newsletter, by sending from my gmail account, I simply do not receive any emails from that [e-mail] at all.

All the forwarded emails show up in the stats as forwarded for their respective alias from the proper sender in my Simplelogin account dashboard.

It wasn't always like this for the alias emails (originating from simplelogin.co). I didn't have problems before, besides sometimes being marked as Spam, which is acceptable, so long as I receive them in my Yahoo mailbox in a timely manner.

I think the official non-alias emails originating from simplelogin.io designated to my Yahoo account is ok
However, I don't know how I would verify that now. I also signed up for the Simpelogin newsletter email and I have yet to receive one single newsletter email.

Note that I can send or reply to a reverse-alias from my Yahoo mailbox, and it gets sent and properly forwarded immediately, receiving it on the gmail side.

So:
gmail --> SL alias --> Yahoo mailbox == massive delay OR never received
But:
Yahoo --> reverse-alias --> gmail == immediate, no problems, not labeled as spam

Regarding that service's newsletter email [e-mail] I mentioned, which after testing, I now never receive anything from on Yahoo, is it possible for the newsletter sender, to somehow mark it as "bad" or blacklist it somehow? Usually it's the recipient's provider that initiates any blacklisting, as far as I understand, but would it be possible for the sender to do so too (although it would be strange in this case after having successfully received it a few times in the past)?

Note: I also tested this with Firefox Relay / Mozilla's mozmail.com aliases and I have no problems receiving forwarded emails to my Yahoo account from there, even now.
i.e.
gmail --> [e-mail] --> Yahoo mailbox
always works

Expected behavior
All emails are forwarded to my Yahoo mailbox in timely manner.

Screenshots
N/A

Environment (If applicable):

• client OS: Linux
• Browser: Firefox, 117.0.1

Additional context
N/A

[Filippo]

Same with me and my gf account. We have both premium version.
I received multiple emails "An email sent to your alias xxx@xxx from xxx was bounced by your mailbox [e-mail]" starting today. Until yesterday I received more than 500 email without problem.
For instance Amazon sent an email to me and it was bounced.

I cannot put a filter like the SL suggestion, it is not possible in yahoo and i cannot mark as not spam since it is bounced before get in. How can I resolve?

[Son Nguyen Kim]

Hi there was an issue with Yahoo mail server, we have reached out to Yahoo admin and they have confirmed that the issue should be fixed now. We are sorry for the inconvenience. If it continues to happen and if it's possible, we'd recommend to use a more reliable email service. SL is in Proton so of course we recommend Proton Mail but from what we see, any serious email service works flawlessly with SL.