Hi, thanks. The problem is that I send the message to their email address #1, and my spam program therefore recognizes #1. Unbeknownst to me, they have #1 set up to forward to #2, and I don’t know about #2. So, when they reply from #2, my spam filter catches it.
Is there a way they can reply from #2, but make it look like it came from #1, without action on my part? Thanks.
Usually mails from big establishments cannot be replied-to directly from the mail address they used to communicate with you.
They often provide a standard reply-to address, or will have enclosed a secure-mail reply link in the first mail they sent you.
Weird-looking mail addresses with lots of gibberish characters and numbers are the kinds of mails that you cannot reply to, directly, using the same address that they used to send the mail with.
Check on the sitemap of the website, they would have listed a helpline number, or email address. Ask them specifically what address you must enter into your spam filter to allow mails from the said establishment.
Put #2 in your white list
It's not entirely clear to me, however, what good that does you. You can't reasonably control how others respond to you, nor can you practically learn all the various ways of setting the apparent sender and then teach all those with whom you correspond to make those changes in their settings.
There is an interesting web page showing the popularity of various email clients at http://gmane.org/user-agents.php. The falling "Mozilla" and the rising "Thunderbird" are different versions of what's pretty much the same client, and could be considered as one. Doing that, the image becomes pretty simple: Google's gmail is rising, and all else is falling. This gmane site is biased toward computer nerds, so under represents ordinary MicroSoft Windows users.