Unfortunately, this is neither perfect (its buggy) nor convenient in many cases. mIRC has issues with the certificate saving, which seems somewhat random, some certificates mirc will simply not save/match against correctly. Not to mention that on networks with many servers you'd have to check /map (if its not disabled) and connect/accept each and every server to avoid future annoyances with reconnection asking to accept the certificate and such... obviously resulting in non-reconnection if you are not at pc at the time.
On top of that, some networks are configured not to allow direct server connection through the servers ip or personal dns, and require you to use one of the dns pool addresses, which makes itterating through them almost impossible (both since you cant do it manually and since continuous reconnections to the dns pool will not garantee you hit all the servers)
I have actually posted/suggested about this a few times (different methods), somewhat disappointed that silly (at least in my opinion) new gui features get implemented yet little time (seemingly) spent to improve/fix/enhance such a core part of the program, but thats how the cookie crumbles and hopefully something will be done eventually.
Links to some prior suggestions:/server -e# to manipulate ssl cert. interactionSafe/Trusted SSL list
There have been others but since they were not by me i cant be sure what to search for to find them.
As a side note, the search feature on these boards seem to limit you to 101 results, so expanding search to 5 years is pointless half the time, you have to search over and over altering the 'older than' values in order to get a decent set of results. This makes the whole 'expand to 5 years' suggestion everybody makes when they talk about users searching the forums pretty much nulled. Chances are they wont get any older than several months/a year anyway due to the result limit.