Does Videotron have a greylist of user IP addresses?

Hello, recently all my emails sent from my home take exactly 6 minutes to reach their destination. It doesn't matter if I use the email client on my PC, my iPad, or even use the Videotron webmail application CourrielWeb, if the email gets sent via my home modem, it gets delayed.

If I move to another residence in another town, emails sent out from that location using my iPad or CourrielWeb pass in seconds. My email account has not changed, only the IP address of the modem at the different residence.

I read today that greylists are used by some internet service providers to slow down, but not totally block, the transmission of emails originating from a source that is under suspicion, but not blacklisted.

Being on an ISP's greylist is reported to cause a fixed transmission delay between 5 and 15 minutes, so it is not surprising that my delays are always exactly 6 minutes.

No one at Videotron support has been able to explain my 6 minute delay, only that a delay of 6 minutes is not unacceptable in a world where email transmission times can vary according to many factors.

So have you ever experienced email transmission symptoms similar to being on a greylist, and if so, how did you resolve your problem?

Thanks for any comments.