Why are chains of letters not coming to the forwarded mailbox?

Question

Email

Hello! There is a hoster's mail with which redirection to a gmail box is set. Single letters come and go - everything is ok with her, but the chains of letters do not reach .. i.e. if a letter is sent to me with a mail attached to the gmail hoster, I receive it, but if I answer with a chain of letters, then the letter no longer reaches the gmail box. If I untie redirection, then in the control panel of mail accounts all letters with chains come.
In the course of communication with the hoster and my own tests, I found out that this is the case in the gmail box, because. Letters definitely come to the account, but I don’t find anything in spam. do not tell me what mail settings it can be connected with?